Support unaligned M

* speedup scalars in cuda

* comment

.circleci/config.yml

@@ -7,18 +7,6 @@ parameters:
   nightly_build:
     type: boolean
     default: false
-  weekly_build:
-    type: boolean
-    default: false
-  test_release:
-    type: boolean
-    default: false
-  linux_release:
-    type: boolean
-    default: false
-  cuda_release:
-    type: boolean
-    default: false
 
 jobs:
   build_documentation:
@@ -41,7 +29,7 @@ jobs:
             pip install --upgrade pip
             pip install --upgrade cmake
             pip install -r docs/requirements.txt
-            CMAKE_BUILD_PARALLEL_LEVEL=`sysctl -n hw.ncpu` pip install . -v
+            pip install . -v
       - when:
           condition:
             not: << parameters.upload-docs >>
@@ -73,9 +61,9 @@ jobs:
                  git push -f origin gh-pages
 
   linux_build_and_test:
-    docker:
-      - image: cimg/python:3.9
-
+    machine:
+      image: ubuntu-2204:current
+      resource_class: large
     steps:
       - checkout
       - run:
@@ -87,21 +75,17 @@ jobs:
       - run:
           name: Install dependencies
           command: |
-            pip install --upgrade cmake
-            pip install nanobind==2.4.0
-            pip install numpy
+            export DEBIAN_FRONTEND=noninteractive
+            export NEEDRESTART_MODE=a
             sudo apt-get update
-            sudo apt-get install libblas-dev liblapack-dev liblapacke-dev
+            sudo apt-get upgrade -y
+            pip install --upgrade cmake
+            sudo apt-get install -y libblas-dev liblapack-dev liblapacke-dev
             sudo apt-get install openmpi-bin openmpi-common libopenmpi-dev
       - run:
           name: Install Python package
           command: |
-            CMAKE_ARGS="-DMLX_BUILD_METAL=OFF" \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
-              python3 setup.py build_ext --inplace
-            CMAKE_ARGS="-DMLX_BUILD_METAL=OFF" \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
-              python3 setup.py develop
+            pip install -e ".[dev]"
       - run:
           name: Generate package stubs
           command: |
@@ -111,9 +95,10 @@ jobs:
       - run:
           name: Run Python tests
           command: |
-            python3 -m unittest discover python/tests -v
+            python -m unittest discover python/tests -v
             mpirun --bind-to none -host localhost:8 -np 8 python python/tests/mpi_test_distributed.py
-            mlx.launch --verbose -n 8 python/tests/ring_test_distributed.py
+            mlx.launch --verbose -n 8 python/tests/ring_test_distributed.py -v 2> >(tee -a stderr.log >&2)
+            if $(grep "\[WARN\]" stderr.log); then echo "Distributed ring test failed"; exit 1; fi
       - run:
           name: Build CPP only
           command: |
@@ -157,8 +142,7 @@ jobs:
           name: Install Python package
           command: |
             source env/bin/activate
-            DEBUG=1 CMAKE_BUILD_PARALLEL_LEVEL=`sysctl -n hw.ncpu` \
-            CMAKE_ARGS="-DCMAKE_COMPILE_WARNING_AS_ERROR=ON" \
+            DEBUG=1 CMAKE_ARGS="-DCMAKE_COMPILE_WARNING_AS_ERROR=ON" \
               pip install -e . -v
       - run:
           name: Generate package stubs
@@ -173,7 +157,8 @@ jobs:
             LOW_MEMORY=1 DEVICE=cpu python -m xmlrunner discover -v python/tests -o test-results/cpu
             LOW_MEMORY=1 DEVICE=gpu METAL_DEVICE_WRAPPER_TYPE=1 METAL_DEBUG_ERROR_MODE=0 python -m xmlrunner discover -v python/tests -o test-results/gpu
             mpirun --bind-to none -host localhost:8 -np 8 -x DYLD_LIBRARY_PATH=/opt/homebrew/lib/ python python/tests/mpi_test_distributed.py
-            mlx.launch --verbose -n 8 python/tests/ring_test_distributed.py
+            mlx.launch --verbose -n 8 python/tests/ring_test_distributed.py -v 2> >(tee -a stderr.log >&2)
+            if $(grep "\[WARN\]" stderr.log); then echo "Distributed ring test failed"; exit 1; fi
       - run:
           name: Build example extension
           command: |
@@ -208,7 +193,6 @@ jobs:
           name: Run Python tests with JIT
           command: |
             source env/bin/activate
-            CMAKE_BUILD_PARALLEL_LEVEL=`sysctl -n hw.ncpu` \
             CMAKE_ARGS="-DMLX_METAL_JIT=ON" \
               pip install -e . -v
             LOW_MEMORY=1 DEVICE=gpu METAL_DEVICE_WRAPPER_TYPE=1 \
@@ -217,7 +201,7 @@ jobs:
 
   cuda_build_and_test:
     machine:
-      image: linux-cuda-12:default
+      image: linux-cuda-12:2023.11.1
       resource_class: gpu.nvidia.small.gen2
     steps:
       - checkout
@@ -226,9 +210,8 @@ jobs:
           command: |
             sudo apt-get update
             sudo apt-get install libblas-dev liblapack-dev liblapacke-dev
-            python -m venv env
+            python3 -m venv env
             source env/bin/activate
-            CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
             CMAKE_ARGS="-DMLX_BUILD_CUDA=ON -DCMAKE_CUDA_COMPILER=`which nvcc`" \
               pip install -e ".[dev]"
       - run:
@@ -278,7 +261,6 @@ jobs:
           command: |
             source env/bin/activate
             env -u MACOSX_DEPLOYMENT_TARGET DEV_RELEASE=1 \
-              CMAKE_BUILD_PARALLEL_LEVEL=`sysctl -n hw.ncpu` \
               pip install . -v
       - run:
           name: Generate package stubs
@@ -290,9 +272,18 @@ jobs:
           name: Build Python package
           command: |
             source env/bin/activate
-            << parameters.build_env >> \
-              CMAKE_BUILD_PARALLEL_LEVEL=`sysctl -n hw.ncpu` \
-              python -m build -w
+            python setup.py clean --all
+            << parameters.build_env >> MLX_BUILD_STAGE=1 python -m build -w
+      - when:
+          condition:
+            equal: ["3.9", << parameters.python_version >>]
+          steps:
+            - run:
+                name: Build common package
+                command: |
+                  source env/bin/activate
+                  python setup.py clean --all
+                  << parameters.build_env >> MLX_BUILD_STAGE=2 python -m build -w
       - when:
           condition: << parameters.build_env >>
           steps:
@@ -309,65 +300,73 @@ jobs:
       python_version:
         type: string
         default: "3.9"
-      extra_env:
+      build_env:
         type: string
-        default: "DEV_RELEASE=1"
-    docker:
-      - image: ubuntu:20.04
+        default: ""
+    machine:
+      image: ubuntu-2204:current
+      resource_class: large
     steps:
       - checkout
       - run:
           name: Build wheel
           command: |
             PYTHON=python<< parameters.python_version >>
-            apt-get update
-            apt-get upgrade -y
-            DEBIAN_FRONTEND=noninteractive TZ=Etc/UTC apt-get -y install tzdata
-            apt-get install -y apt-utils
-            apt-get install -y software-properties-common
-            add-apt-repository -y ppa:deadsnakes/ppa
-            apt-get install -y $PYTHON $PYTHON-dev $PYTHON-full
-            apt-get install -y libblas-dev liblapack-dev liblapacke-dev
-            apt-get install -y build-essential git
+            export DEBIAN_FRONTEND=noninteractive
+            export NEEDRESTART_MODE=a
+            sudo apt-get update
+            sudo apt-get upgrade -y
+            TZ=Etc/UTC sudo apt-get -y install tzdata
+            sudo apt-get install -y apt-utils
+            sudo apt-get install -y software-properties-common
+            sudo add-apt-repository -y ppa:deadsnakes/ppa
+            sudo apt-get install -y $PYTHON $PYTHON-dev $PYTHON-full
+            sudo apt-get install -y libblas-dev liblapack-dev liblapacke-dev
+            sudo apt-get install -y build-essential git
             $PYTHON -m venv env
             source env/bin/activate
             pip install --upgrade pip
             pip install --upgrade cmake
-            pip install nanobind==2.4.0
-            pip install --upgrade setuptools
-            pip install numpy
             pip install auditwheel
             pip install patchelf
             pip install build
             pip install twine
-            << parameters.extra_env >> \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
-              pip install . -v
+            << parameters.build_env >> pip install ".[dev]" -v
             pip install typing_extensions
             python setup.py generate_stubs
-            << parameters.extra_env >> \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
-              python -m build --wheel
-            auditwheel show dist/*
-            auditwheel repair dist/* --plat manylinux_2_31_x86_64
+            python setup.py clean --all
+            MLX_BUILD_STAGE=1 << parameters.build_env >> python -m build -w
+            bash python/scripts/repair_linux.sh
+      - when:
+          condition:
+            equal: ["3.9", << parameters.python_version >>]
+          steps:
             - run:
-          name: Upload package
+                name: Build common package
                 command: |
                   source env/bin/activate
-            twine upload wheelhouse/*
+                  python setup.py clean --all
+                  << parameters.build_env >> MLX_BUILD_STAGE=2 \
+                    python -m build -w
+                  auditwheel repair dist/mlx_cpu*.whl --plat manylinux_2_35_x86_64
+      - when:
+          condition: << parameters.build_env >>
+          steps:
+            - run:
+                name: Upload packages
+                command: |
+                  source env/bin/activate
+                  twine upload wheelhouse/*.whl
       - store_artifacts:
           path: wheelhouse/
 
   build_cuda_release:
     parameters:
-      python_version:
+      build_env:
         type: string
-        default: "3.9"
-      extra_env:
-        type: string
-        default: "DEV_RELEASE=1"
+        default: ""
     machine:
-      image: linux-cuda-12:default
+      image: linux-cuda-12:2024.11.1
       resource_class: gpu.nvidia.small.gen2
     steps:
       - checkout
@@ -376,22 +375,20 @@ jobs:
           command: |
             sudo apt-get update
             sudo apt-get install libblas-dev liblapack-dev liblapacke-dev
+            sudo apt-get install zip
             python -m venv env
             source env/bin/activate
             pip install auditwheel
             pip install patchelf
             pip install build
             pip install twine
-            << parameters.extra_env >> \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
+            << parameters.build_env >> MLX_BUILD_STAGE=2 \
               CMAKE_ARGS="-DMLX_BUILD_CUDA=ON -DCMAKE_CUDA_COMPILER=`which nvcc`" \
-              pip install ".[dev]" -v
-            python setup.py generate_stubs
-            << parameters.extra_env >> \
-              CMAKE_BUILD_PARALLEL_LEVEL=`nproc` \
-              CMAKE_ARGS="-DMLX_BUILD_CUDA=ON -DCMAKE_CUDA_COMPILER=`which nvcc`" \
-              python -m build --wheel
+              python -m build -w
             bash python/scripts/repair_cuda.sh
+      - when:
+          condition: << parameters.build_env >>
+          steps:
             - run:
                 name: Upload package
                 command: |
@@ -408,8 +405,6 @@ workflows:
             pattern: "^(?!pull/)[-\\w]+$"
             value: << pipeline.git.branch >>
         - not: << pipeline.parameters.nightly_build >>
-        - not: << pipeline.parameters.weekly_build >>
-        - not: << pipeline.parameters.test_release >>
     jobs:
       - mac_build_and_test:
           matrix:
@@ -423,8 +418,6 @@ workflows:
     when:
       and:
         - not: << pipeline.parameters.nightly_build >>
-        - not: << pipeline.parameters.weekly_build >>
-        - not: << pipeline.parameters.test_release >>
     jobs:
       - build_release:
           filters:
@@ -506,6 +499,25 @@ workflows:
             branches:
               ignore: /.*/
           upload-docs: true
+      - build_linux_release:
+          filters:
+            tags:
+              only: /^v.*/
+            branches:
+              ignore: /.*/
+          matrix:
+            parameters:
+              python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+              build_env: ["PYPI_RELEASE=1"]
+      - build_cuda_release:
+          filters:
+            tags:
+              only: /^v.*/
+            branches:
+              ignore: /.*/
+          matrix:
+            parameters:
+              build_env: ["PYPI_RELEASE=1"]
 
   prb:
     when:
@@ -584,99 +596,8 @@ workflows:
               - macosx_deployment_target: "15.0"
                 xcode_version: "15.0.0"
                 python_version: "3.13"
-  weekly_build:
-    when:
-      and:
-        - equal: [ main, << pipeline.git.branch >> ]
-        - << pipeline.parameters.weekly_build >>
-    jobs:
-      - build_release:
-          matrix:
-            parameters:
-              python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
-              macosx_deployment_target: ["13.5", "14.0", "15.0"]
-              build_env: ["DEV_RELEASE=1"]
-              xcode_version: ["16.2.0", "15.0.0"]
-            exclude:
-              - macosx_deployment_target: "13.5"
-                xcode_version: "16.2.0"
-                python_version: "3.9"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "13.5"
-                xcode_version: "16.2.0"
-                python_version: "3.10"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "13.5"
-                xcode_version: "16.2.0"
-                python_version: "3.11"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "13.5"
-                xcode_version: "16.2.0"
-                python_version: "3.12"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "13.5"
-                xcode_version: "16.2.0"
-                python_version: "3.13"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "14.0"
-                xcode_version: "15.0.0"
-                python_version: "3.9"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "14.0"
-                xcode_version: "15.0.0"
-                python_version: "3.10"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "14.0"
-                xcode_version: "15.0.0"
-                python_version: "3.11"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "14.0"
-                xcode_version: "15.0.0"
-                python_version: "3.12"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "14.0"
-                xcode_version: "15.0.0"
-                python_version: "3.13"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "15.0"
-                xcode_version: "15.0.0"
-                python_version: "3.9"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "15.0"
-                xcode_version: "15.0.0"
-                python_version: "3.10"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "15.0"
-                xcode_version: "15.0.0"
-                python_version: "3.11"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "15.0"
-                xcode_version: "15.0.0"
-                python_version: "3.12"
-                build_env: "DEV_RELEASE=1"
-              - macosx_deployment_target: "15.0"
-                xcode_version: "15.0.0"
-                python_version: "3.13"
-                build_env: "DEV_RELEASE=1"
-  linux_test_release:
-    when:
-      and:
-        - equal: [ main, << pipeline.git.branch >> ]
-        - << pipeline.parameters.linux_release >>
-    jobs:
       - build_linux_release:
           matrix:
             parameters:
               python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
-              extra_env: ["PYPI_RELEASE=1"]
-  cuda_test_release:
-    when:
-      and:
-        - equal: [ main, << pipeline.git.branch >> ]
-        - << pipeline.parameters.cuda_release >>
-    jobs:
-      - build_cuda_release:
-          matrix:
-            parameters:
-              python_version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
-              extra_env: ["PYPI_RELEASE=1"]
+      - build_cuda_release

ACKNOWLEDGMENTS.md

@@ -19,6 +19,7 @@ MLX was developed with contributions from the following individuals:
 - Gleb Pobudzey: Added the `where` primitive, and groups in 1D and 2D convolutions.
 - Paul Paczuski: Improved stability of BCE loss calculation
 - Max-Heinrich Laves: Added `conv_transpose1d`, `conv_transpose2d`, and `conv_transpose3d` ops.
+- Gökdeniz Gülmez: Added the `Muon (MomentUm Orthogonalized by Newton-schulz)` optimizer.
 
 <a href="https://github.com/ml-explore/mlx/graphs/contributors">
   <img class="dark-light" src="https://contrib.rocks/image?repo=ml-explore/mlx&anon=0&columns=20&max=100&r=true" />

CMakeLists.txt

@@ -22,7 +22,7 @@ project(
 
 # ----------------------------- Setup -----------------------------
 set(CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake")
-set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD 20)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 set(CMAKE_INSTALL_MESSAGE NEVER)
@@ -64,10 +64,8 @@ if(${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
       message(WARNING "Building for x86_64 arch is not officially supported.")
     endif()
   endif()
-
 else()
   set(MLX_BUILD_METAL OFF)
-  message(WARNING "MLX is prioritised for Apple silicon systems using macOS.")
 endif()
 
 # ----------------------------- Lib -----------------------------

benchmarks/cpp/single_ops.cpp

@@ -193,8 +193,8 @@ void time_reductions() {
   auto argmin_along_1 = [&a]() { return mx::argmin(a, 1, false); };
   TIME(argmin_along_1);
 
-  auto indices = mlx::core::array({1});
-  auto updates = mlx::core::reshape(mlx::core::array({NAN}), {1, 1, 1});
+  auto indices = mx::array({1});
+  auto updates = mx::reshape(mx::array({NAN}), {1, 1, 1});
   std::vector<int> axes{0};
   auto b = scatter(a, {indices}, updates, axes);
   mx::eval(b);
@@ -203,6 +203,11 @@ void time_reductions() {
   TIME(max_along_0);
   auto max_along_1 = [&b]() { return mx::max(b, 1, false); };
   TIME(max_along_1);
+
+  auto min_along_0 = [&b]() { return mx::min(b, 0, false); };
+  TIME(min_along_0);
+  auto min_along_1 = [&b]() { return mx::min(b, 1, false); };
+  TIME(min_along_1);
 }
 
 void time_gather_scatter() {

benchmarks/python/single_ops.py

@@ -58,6 +58,13 @@ def time_max():
     time_fn(mx.max, a, 0)
 
 
+def time_min():
+    a = mx.random.uniform(shape=(32, 1024, 1024))
+    a[1, 1] = mx.nan
+    mx.eval(a)
+    time_fn(mx.min, a, 0)
+
+
 def time_negative():
     a = mx.random.uniform(shape=(10000, 1000))
     mx.eval(a)
@@ -115,6 +122,7 @@ if __name__ == "__main__":
 
     time_add()
     time_matmul()
+    time_min()
     time_max()
     time_maximum()
     time_exp()

docs/src/dev/extensions.rst

@@ -138,13 +138,13 @@ more concrete:
         * representing the vectorized computation and the axis which
         * corresponds to the output vectorized dimension.
         */
-        virtual std::pair<std::vector<array>, std::vector<int>> vmap(
+        std::pair<std::vector<array>, std::vector<int>> vmap(
             const std::vector<array>& inputs,
             const std::vector<int>& axes) override;
 
-        /** Print the primitive. */
-        void print(std::ostream& os) override {
-            os << "Axpby";
+        /** The name of primitive. */
+        const char* name() const override {
+          return "Axpby";
         }
 
         /** Equivalence check **/

docs/src/install.rst

@@ -23,13 +23,6 @@ To install from PyPI you must meet the following requirements:
     MLX is only available on devices running macOS >= 13.5
     It is highly recommended to use macOS 14 (Sonoma)
 
-
-MLX is also available on conda-forge. To install MLX with conda do:
-
-.. code-block:: shell
-
-   conda install conda-forge::mlx
-
 CUDA
 ^^^^
 
@@ -38,8 +31,16 @@ and SM 7.0 (Volta) and up. To install MLX with CUDA support, run:
 
 .. code-block:: shell
 
-    pip install mlx-cuda
+    pip install "mlx[cuda]"
 
+CPU-only (Linux)
+^^^^^^^^^^^^^^^^
+
+For a CPU-only version of MLX that runs on Linux use:
+
+.. code-block:: shell
+
+    pip install "mlx[cpu]"
 
 Troubleshooting
 ^^^^^^^^^^^^^^^
@@ -88,20 +89,20 @@ Then simply build and install MLX using pip:
 
 .. code-block:: shell
 
-  CMAKE_BUILD_PARALLEL_LEVEL=8 pip install .
+  pip install .
 
 For developing, install the package with development dependencies, and use an
 editable install:
 
 .. code-block:: shell
 
-  CMAKE_BUILD_PARALLEL_LEVEL=8 pip install -e ".[dev]"
+  pip install -e ".[dev]"
 
 Once the development dependencies are installed, you can build faster with:
 
 .. code-block:: shell
 
- CMAKE_BUILD_PARALLEL_LEVEL=8 python setup.py build_ext --inplace
+ python setup.py build_ext --inplace
 
 Run the tests with:
 
@@ -262,7 +263,7 @@ When building either the Python or C++ APIs make sure to pass the cmake flag
 
 .. code-block:: shell
 
-  CMAKE_BUILD_PARALLEL_LEVEL=8 CMAKE_ARGS="-DMLX_BUILD_CUDA=ON" pip install -e ".[dev]"
+  CMAKE_ARGS="-DMLX_BUILD_CUDA=ON" pip install -e ".[dev]"
 
 To build the C++ package run:
 

docs/src/python/optimizers/common_optimizers.rst

@@ -19,3 +19,4 @@ Common Optimizers
    Adamax
    Lion
    MultiOptimizer
+   Muon

examples/extensions/axpby/axpby.h

@@ -74,9 +74,9 @@ class Axpby : public mx::Primitive {
       const std::vector<mx::array>& inputs,
       const std::vector<int>& axes) override;
 
-  /** Print the primitive. */
-  void print(std::ostream& os) override {
-    os << "Axpby";
+  /** The name of primitive. */
+  const char* name() const override {
+    return "Axpby";
   }
 
   /** Equivalence check **/

mlx/backend/common/utils.cpp

@@ -1,14 +1,20 @@
 // Copyright © 2023-2024 Apple Inc.
 
+#include <dlfcn.h>
+
 #include "mlx/backend/common/utils.h"
-#include "mlx/primitives.h"
 
 namespace mlx::core {
 
-std::string get_primitive_string(Primitive* primitive) {
-  std::ostringstream op_t;
-  primitive->print(op_t);
-  return op_t.str();
+std::filesystem::path current_binary_dir() {
+  static std::filesystem::path binary_dir = []() {
+    Dl_info info;
+    if (!dladdr(reinterpret_cast<void*>(&current_binary_dir), &info)) {
+      throw std::runtime_error("Unable to get current binary dir.");
+    }
+    return std::filesystem::path(info.dli_fname).parent_path();
+  }();
+  return binary_dir;
 }
 
 std::tuple<Shape, std::vector<Strides>> collapse_contiguous_dims(

mlx/backend/common/utils.h

@@ -2,6 +2,7 @@
 
 #pragma once
 
+#include <filesystem>
 #include <tuple>
 #include <vector>
 
@@ -9,7 +10,8 @@
 
 namespace mlx::core {
 
-std::string get_primitive_string(Primitive* primitive);
+// Return the directory that contains current shared library.
+std::filesystem::path current_binary_dir();
 
 inline int64_t
 elem_to_loc(int elem, const Shape& shape, const Strides& strides) {

mlx/backend/cpu/cholesky.cpp

@@ -20,7 +20,7 @@ void cholesky_impl(const array& a, array& factor, bool upper, Stream stream) {
 
   // The decomposition is computed in place, so just copy the input to the
   // output.
-  copy(
+  copy_cpu(
       a,
       factor,
       a.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cpu/compiled.cpp

@@ -231,7 +231,7 @@ inline void build_kernel(
       os << "static_cast<" << get_type_string(x.dtype()) << ">(tmp_"
          << namer.get_name(x.inputs()[0]) << ");" << std::endl;
     } else {
-      x.primitive().print(os);
+      os << x.primitive().name();
       os << "()(";
       for (int i = 0; i < x.inputs().size() - 1; i++) {
         os << "tmp_" << namer.get_name(x.inputs()[i]) << ", ";

mlx/backend/cpu/conv.cpp

@@ -883,7 +883,7 @@ void explicit_gemm_conv_1D_cpu(
   // Fill with zeros
   std::vector<array> temps;
   temps.push_back(array(0, conv_dtype));
-  copy(temps.back(), in_padded, CopyType::Scalar, stream);
+  copy_cpu(temps.back(), in_padded, CopyType::Scalar, stream);
 
   // Pick input slice from padded
   size_t data_offset = padding_lo[0] * in_padded.strides()[1];
@@ -895,7 +895,7 @@ void explicit_gemm_conv_1D_cpu(
       in_padded_slice.size(),
       data_offset);
   // Copy input values into the slice
-  copy_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
+  copy_cpu_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
   temps.push_back(in_padded_slice);
 
   // Make strided view
@@ -920,7 +920,7 @@ void explicit_gemm_conv_1D_cpu(
   // Materialize strided view
   Shape strided_reshape = {N * oH, wH * C};
   array in_strided(strided_reshape, in_strided_view.dtype(), nullptr, {});
-  copy(in_strided_view, in_strided, CopyType::General, stream);
+  copy_cpu(in_strided_view, in_strided, CopyType::General, stream);
   temps.push_back(in_strided);
 
   // Check wt dtype and prepare
@@ -938,13 +938,13 @@ void explicit_gemm_conv_1D_cpu(
         wt.size(),
         0);
     gemm_wt = array(wt_transpose.shape(), float32, nullptr, {});
-    copy(wt_transpose, gemm_wt, CopyType::General, stream);
+    copy_cpu(wt_transpose, gemm_wt, CopyType::General, stream);
     temps.push_back(gemm_wt);
   } else if (wt.dtype() != float32 || !wt.flags().row_contiguous) {
     auto ctype =
         wt.flags().row_contiguous ? CopyType::Vector : CopyType::General;
     gemm_wt = array(wt.shape(), float32, nullptr, {});
-    copy(wt, gemm_wt, ctype, stream);
+    copy_cpu(wt, gemm_wt, ctype, stream);
     temps.push_back(gemm_wt);
   }
 
@@ -991,7 +991,7 @@ void explicit_gemm_conv_1D_cpu(
 
   // Copy results if needed
   if (out.dtype() != float32) {
-    copy_inplace(gemm_out, out, CopyType::Vector, stream);
+    copy_cpu_inplace(gemm_out, out, CopyType::Vector, stream);
   }
   encoder.add_temporaries(std::move(temps));
 }
@@ -1029,7 +1029,7 @@ void explicit_gemm_conv_2D_cpu(
   // Fill with zeros
   std::vector<array> temps;
   temps.push_back(array(0, conv_dtype));
-  copy(temps.back(), in_padded, CopyType::Scalar, stream);
+  copy_cpu(temps.back(), in_padded, CopyType::Scalar, stream);
 
   // Pick input slice from padded
   size_t data_offset = padding_lo[0] * in_padded.strides()[1] +
@@ -1044,7 +1044,7 @@ void explicit_gemm_conv_2D_cpu(
   temps.push_back(in_padded_slice);
 
   // Copy input values into the slice
-  copy_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
+  copy_cpu_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
 
   // Make strided view
   Shape strided_shape = {N, oH, oW, wH, wW, C};
@@ -1065,7 +1065,7 @@ void explicit_gemm_conv_2D_cpu(
   // Materialize strided view
   Shape strided_reshape = {N * oH * oW, wH * wW * C};
   array in_strided(strided_reshape, in_strided_view.dtype(), nullptr, {});
-  copy(in_strided_view, in_strided, CopyType::General, stream);
+  copy_cpu(in_strided_view, in_strided, CopyType::General, stream);
   temps.push_back(in_strided);
 
   // Check wt dtype and prepare
@@ -1076,7 +1076,7 @@ void explicit_gemm_conv_2D_cpu(
     auto ctype =
         wt.flags().row_contiguous ? CopyType::Vector : CopyType::General;
     gemm_wt = array(wt.shape(), float32, nullptr, {});
-    copy(wt, gemm_wt, ctype, stream);
+    copy_cpu(wt, gemm_wt, ctype, stream);
     temps.push_back(gemm_wt);
   }
 
@@ -1116,7 +1116,7 @@ void explicit_gemm_conv_2D_cpu(
 
   // Copy results if needed
   if (out.dtype() != float32) {
-    copy_inplace(gemm_out, out, CopyType::Vector, stream);
+    copy_cpu_inplace(gemm_out, out, CopyType::Vector, stream);
   }
   encoder.add_temporaries(std::move(temps));
 }
@@ -1156,7 +1156,7 @@ void explicit_gemm_conv_ND_cpu(
 
   // Fill with zeros
   std::vector<array> temps = {array(0, conv_dtype)};
-  copy(temps.back(), in_padded, CopyType::Scalar, stream);
+  copy_cpu(temps.back(), in_padded, CopyType::Scalar, stream);
 
   // Pick input slice from padded
   size_t data_offset = 0;
@@ -1173,7 +1173,7 @@ void explicit_gemm_conv_ND_cpu(
       data_offset);
 
   // Copy input values into the slice
-  copy_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
+  copy_cpu_inplace(in, in_padded_slice, CopyType::GeneralGeneral, stream);
   temps.push_back(in_padded_slice);
 
   // Make strided view
@@ -1212,7 +1212,7 @@ void explicit_gemm_conv_ND_cpu(
   }
 
   array in_strided(strided_reshape, in_strided_view.dtype(), nullptr, {});
-  copy(in_strided_view, in_strided, CopyType::General, stream);
+  copy_cpu(in_strided_view, in_strided, CopyType::General, stream);
   temps.push_back(in_strided);
 
   // Check wt dtype and prepare
@@ -1223,13 +1223,13 @@ void explicit_gemm_conv_ND_cpu(
     auto ctype =
         wt.flags().row_contiguous ? CopyType::Vector : CopyType::General;
     gemm_wt = array(wt.shape(), float32, nullptr, {});
-    copy(wt, gemm_wt, ctype, stream);
+    copy_cpu(wt, gemm_wt, ctype, stream);
     temps.push_back(gemm_wt);
   }
 
   if (flip) {
     auto gemm_wt_ = array(gemm_wt.shape(), float32, nullptr, {});
-    copy(gemm_wt, gemm_wt_, CopyType::Vector, stream);
+    copy_cpu(gemm_wt, gemm_wt_, CopyType::Vector, stream);
     temps.push_back(gemm_wt_);
 
     // Calculate the total size of the spatial dimensions
@@ -1284,7 +1284,7 @@ void explicit_gemm_conv_ND_cpu(
 
   // Copy results if needed
   if (out.dtype() != float32) {
-    copy_inplace(gemm_out, out, CopyType::Vector, stream);
+    copy_cpu_inplace(gemm_out, out, CopyType::Vector, stream);
   }
   encoder.add_temporaries(std::move(temps));
 }

mlx/backend/cpu/copy.cpp

@@ -295,7 +295,11 @@ inline void copy_inplace_dispatch(
 
 } // namespace
 
-void copy_inplace(const array& src, array& dst, CopyType ctype, Stream stream) {
+void copy_cpu_inplace(
+    const array& src,
+    array& dst,
+    CopyType ctype,
+    Stream stream) {
   auto& encoder = cpu::get_command_encoder(stream);
   encoder.set_input_array(src);
   encoder.set_output_array(dst);
@@ -305,7 +309,7 @@ void copy_inplace(const array& src, array& dst, CopyType ctype, Stream stream) {
        ctype]() mutable { copy_inplace_dispatch(src, dst, ctype); });
 }
 
-void copy(const array& src, array& dst, CopyType ctype, Stream stream) {
+void copy_cpu(const array& src, array& dst, CopyType ctype, Stream stream) {
   bool donated = set_copy_output_data(src, dst, ctype);
   if (donated && src.dtype() == dst.dtype()) {
     // If the output has the same type as the input then there is nothing to
@@ -315,10 +319,10 @@ void copy(const array& src, array& dst, CopyType ctype, Stream stream) {
   if (ctype == CopyType::GeneralGeneral) {
     ctype = CopyType::General;
   }
-  copy_inplace(src, dst, ctype, stream);
+  copy_cpu_inplace(src, dst, ctype, stream);
 }
 
-void copy_inplace(
+void copy_cpu_inplace(
     const array& src,
     array& dst,
     const Shape& data_shape,

mlx/backend/cpu/copy.h

@@ -10,10 +10,14 @@
 
 namespace mlx::core {
 
-void copy(const array& src, array& dst, CopyType ctype, Stream stream);
-void copy_inplace(const array& src, array& dst, CopyType ctype, Stream stream);
+void copy_cpu(const array& src, array& dst, CopyType ctype, Stream stream);
+void copy_cpu_inplace(
+    const array& src,
+    array& dst,
+    CopyType ctype,
+    Stream stream);
 
-void copy_inplace(
+void copy_cpu_inplace(
     const array& src,
     array& dst,
     const Shape& data_shape,

mlx/backend/cpu/distributed.cpp

@@ -14,7 +14,7 @@ std::pair<array, bool> ensure_row_contiguous(const array& arr, Stream stream) {
     return {arr, false};
   } else {
     array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-    copy(arr, arr_copy, CopyType::General, stream);
+    copy_cpu(arr, arr_copy, CopyType::General, stream);
     return {arr_copy, true};
   }
 };
@@ -35,7 +35,7 @@ void AllReduce::eval_cpu(
       return in;
     } else {
       array arr_copy(in.shape(), in.dtype(), nullptr, {});
-      copy(in, arr_copy, CopyType::General, s);
+      copy_cpu(in, arr_copy, CopyType::General, s);
       out.copy_shared_buffer(arr_copy);
       return arr_copy;
     }

mlx/backend/cpu/eig.cpp

@@ -135,7 +135,7 @@ void Eig::eval_cpu(
       : array(a.shape(), complex64, nullptr, {});
 
   auto a_copy = array(a.shape(), a.dtype(), nullptr, {});
-  copy(
+  copy_cpu(
       a,
       a_copy,
       a.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cpu/eigh.cpp

@@ -196,7 +196,7 @@ void Eigh::eval_cpu(
 
   values.set_data(allocator::malloc(values.nbytes()));
 
-  copy(
+  copy_cpu(
       a,
       vectors,
       a.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cpu/hadamard.cpp

@@ -96,7 +96,7 @@ void Hadamard::eval_cpu(const std::vector<array>& inputs, array& out) {
   if (in.flags().row_contiguous && in.is_donatable()) {
     out.copy_shared_buffer(in);
   } else {
-    copy(
+    copy_cpu(
         in,
         out,
         in.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cpu/indexing.cpp

@@ -517,7 +517,7 @@ void Scatter::eval_cpu(const std::vector<array>& inputs, array& out) {
   // Copy src into out (copy allocates memory for out)
   auto ctype =
       src.flags().row_contiguous ? CopyType::Vector : CopyType::General;
-  copy(src, out, ctype, stream());
+  copy_cpu(src, out, ctype, stream());
 
   auto& encoder = cpu::get_command_encoder(stream());
   std::vector<array> inds;
@@ -686,7 +686,7 @@ void ScatterAxis::eval_cpu(const std::vector<array>& inputs, array& out) {
   // Copy src into out (copy allocates memory for out)
   auto ctype =
       src.flags().row_contiguous ? CopyType::Vector : CopyType::General;
-  copy(src, out, ctype, stream());
+  copy_cpu(src, out, ctype, stream());
 
   auto& encoder = cpu::get_command_encoder(stream());
   encoder.set_input_array(idx);

mlx/backend/cpu/inverse.cpp

@@ -115,7 +115,7 @@ void inverse_impl(
   //   (A⁻¹)ᵀ = (Aᵀ)⁻¹
 
   // The inverse is computed in place, so just copy the input to the output.
-  copy(
+  copy_cpu(
       a,
       inv,
       a.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cpu/logsumexp.cpp

@@ -88,7 +88,7 @@ void LogSumExp::eval_cpu(const std::vector<array>& inputs, array& out) {
       return x;
     } else {
       auto x_copy = array(x.shape(), x.dtype(), nullptr, {});
-      copy(x, x_copy, CopyType::General, s);
+      copy_cpu(x, x_copy, CopyType::General, s);
       encoder.add_temporary(x_copy);
       return x_copy;
     }

mlx/backend/cpu/luf.cpp

@@ -31,7 +31,7 @@ void luf_impl(
   strides[ndim - 1] = M;
   strides[ndim - 2] = 1;
   lu.set_data(allocator::malloc(lu.nbytes()), lu.nbytes(), strides, flags);
-  copy_inplace(
+  copy_cpu_inplace(
       a,
       lu,
       a.shape(),

mlx/backend/cpu/masked_mm.cpp

@@ -6,6 +6,7 @@
 #include "mlx/backend/common/utils.h"
 #include "mlx/backend/cpu/copy.h"
 #include "mlx/backend/cpu/encoder.h"
+#include "mlx/backend/cpu/gemm.h"
 #include "mlx/backend/cpu/lapack.h"
 #include "mlx/primitives.h"
 
@@ -52,6 +53,58 @@ inline void mask_matrix(
   }
 }
 
+template <typename T>
+inline void segmented_mm(
+    const T* a,
+    const T* b,
+    const uint32_t* segments,
+    T* out,
+    bool a_transposed,
+    bool b_transposed,
+    size_t lda,
+    size_t ldb,
+    const Shape& a_shape,
+    const Strides& a_strides,
+    const Shape& b_shape,
+    const Strides& b_strides,
+    size_t num_segments,
+    const Shape& segments_shape,
+    const Strides& segments_strides) {
+  int ndim = a_shape.size();
+  Shape a_copy = a_shape;
+  Shape b_copy = b_shape;
+  int32_t M = a_copy[ndim - 2];
+  int32_t N = b_copy[ndim - 1];
+  for (int i = 0; i < num_segments; i++) {
+    uint32_t k_start =
+        segments[elem_to_loc(2 * i, segments_shape, segments_strides)];
+    uint32_t k_end =
+        segments[elem_to_loc(2 * i + 1, segments_shape, segments_strides)];
+    if (k_end <= k_start) {
+      std::fill_n(out + i * M * N, M * N, T(0));
+      continue;
+    }
+    a_copy[ndim - 1] = k_end - k_start;
+    b_copy[ndim - 2] = k_end - k_start;
+    matmul<T>(
+        a + k_start * a_strides[ndim - 1],
+        b + k_start * b_strides[ndim - 2],
+        out + i * M * N,
+        a_transposed,
+        b_transposed,
+        lda,
+        ldb,
+        N,
+        1.0,
+        0.0,
+        1,
+        a_copy,
+        a_strides,
+        b_copy,
+        b_strides);
+  }
+}
+
 } // namespace
 
 void BlockMaskedMM::eval_cpu(const std::vector<array>& inputs, array& out) {
@@ -71,20 +124,20 @@ void BlockMaskedMM::eval_cpu(const std::vector<array>& inputs, array& out) {
         if (!expand_all && stx == arr.shape(-1) && sty == 1) {
           if (do_copy) {
             array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-            copy(arr, arr_copy, CopyType::Vector, s);
+            copy_cpu(arr, arr_copy, CopyType::Vector, s);
             return std::make_tuple(false, stx, arr_copy, true);
           }
           return std::make_tuple(false, stx, arr, false);
         } else if (!expand_all && stx == 1 && sty == arr.shape(-2)) {
           if (do_copy) {
             array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-            copy(arr, arr_copy, CopyType::Vector, s);
+            copy_cpu(arr, arr_copy, CopyType::Vector, s);
             return std::make_tuple(true, sty, arr_copy, true);
           }
           return std::make_tuple(true, sty, arr, false);
         } else {
           array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-          copy(arr, arr_copy, CopyType::General, s);
+          copy_cpu(arr, arr_copy, CopyType::General, s);
           int64_t stx = arr.shape(-1);
           return std::make_tuple(false, stx, arr_copy, true);
         }
@@ -333,7 +386,7 @@ void GatherMM::eval_cpu(const std::vector<array>& inputs, array& out) {
       return std::make_tuple(true, sty, arr);
     } else {
       temps.push_back(array(arr.shape(), arr.dtype(), nullptr, {}));
-      copy(arr, temps.back(), CopyType::General, s);
+      copy_cpu(arr, temps.back(), CopyType::General, s);
       int64_t stx = arr.shape(-1);
       return std::make_tuple(false, stx, temps.back());
     }
@@ -437,4 +490,121 @@ void GatherMM::eval_cpu(const std::vector<array>& inputs, array& out) {
   encoder.add_temporaries(std::move(temps));
 }
 
+void SegmentedMM::eval_cpu(const std::vector<array>& inputs, array& out) {
+  out.set_data(allocator::malloc(out.nbytes()));
+
+  auto& s = stream();
+  auto& encoder = cpu::get_command_encoder(stream());
+  auto check_transpose = [&s, &encoder](const array& x) {
+    auto stx = x.strides()[x.ndim() - 2];
+    auto sty = x.strides()[x.ndim() - 1];
+    if (stx == x.shape(-1) && sty == 1) {
+      return std::make_tuple(false, stx, x);
+    } else if (stx == 1 && sty == x.shape(-2)) {
+      return std::make_tuple(true, sty, x);
+    } else {
+      array xc(x.shape(), x.dtype(), nullptr, {});
+      copy_cpu(x, xc, CopyType::General, s);
+      encoder.add_temporary(xc);
+      int64_t stx = x.shape(-1);
+      return std::make_tuple(false, stx, xc);
+    }
+  };
+
+  auto [a_transposed, lda, a] = check_transpose(inputs[0]);
+  auto [b_transposed, ldb, b] = check_transpose(inputs[1]);
+  auto& segments = inputs[2];
+
+  encoder.set_input_array(a);
+  encoder.set_input_array(b);
+  encoder.set_input_array(segments);
+  encoder.set_output_array(out);
+  encoder.dispatch([a = array::unsafe_weak_copy(a),
+                    b = array::unsafe_weak_copy(b),
+                    segments = array::unsafe_weak_copy(segments),
+                    out_ptr = out.data<void>(),
+                    a_transposed = a_transposed,
+                    b_transposed = b_transposed,
+                    lda = lda,
+                    ldb = ldb]() {
+    switch (a.dtype()) {
+      case float64:
+        segmented_mm<double>(
+            a.data<double>(),
+            b.data<double>(),
+            segments.data<uint32_t>(),
+            static_cast<double*>(out_ptr),
+            a_transposed,
+            b_transposed,
+            lda,
+            ldb,
+            a.shape(),
+            a.strides(),
+            b.shape(),
+            b.strides(),
+            segments.size() / 2,
+            segments.shape(),
+            segments.strides());
+        break;
+      case float32:
+        segmented_mm<float>(
+            a.data<float>(),
+            b.data<float>(),
+            segments.data<uint32_t>(),
+            static_cast<float*>(out_ptr),
+            a_transposed,
+            b_transposed,
+            lda,
+            ldb,
+            a.shape(),
+            a.strides(),
+            b.shape(),
+            b.strides(),
+            segments.size() / 2,
+            segments.shape(),
+            segments.strides());
+        break;
+      case float16:
+        segmented_mm<float16_t>(
+            a.data<float16_t>(),
+            b.data<float16_t>(),
+            segments.data<uint32_t>(),
+            static_cast<float16_t*>(out_ptr),
+            a_transposed,
+            b_transposed,
+            lda,
+            ldb,
+            a.shape(),
+            a.strides(),
+            b.shape(),
+            b.strides(),
+            segments.size() / 2,
+            segments.shape(),
+            segments.strides());
+        break;
+      case bfloat16:
+        segmented_mm<bfloat16_t>(
+            a.data<bfloat16_t>(),
+            b.data<bfloat16_t>(),
+            segments.data<uint32_t>(),
+            static_cast<bfloat16_t*>(out_ptr),
+            a_transposed,
+            b_transposed,
+            lda,
+            ldb,
+            a.shape(),
+            a.strides(),
+            b.shape(),
+            b.strides(),
+            segments.size() / 2,
+            segments.shape(),
+            segments.strides());
+        break;
+      default:
+        throw std::invalid_argument(
+            "Segmented mm supports only real float types.");
+    }
+  });
+}
+
 } // namespace mlx::core

mlx/backend/cpu/matmul.cpp

@@ -81,7 +81,7 @@ void matmul_general(
       return std::make_tuple(true, sty, arr);
     } else {
       temps.push_back(array(arr.shape(), arr.dtype(), nullptr, {}));
-      copy(arr, temps.back(), CopyType::General, stream);
+      copy_cpu(arr, temps.back(), CopyType::General, stream);
       stx = arr.shape(-1);
       return std::make_tuple(false, stx, temps.back());
     }
@@ -142,7 +142,7 @@ void AddMM::eval_cpu(const std::vector<array>& inputs, array& out) {
   CopyType ctype = c.data_size() == 1
       ? CopyType::Scalar
       : (c.flags().row_contiguous ? CopyType::Vector : CopyType::General);
-  copy(c, out, ctype, stream());
+  copy_cpu(c, out, ctype, stream());
   if (inputs[0].shape(-1) == 0) {
     return;
   }

mlx/backend/cpu/primitives.cpp

@@ -22,7 +22,7 @@ void reshape(const array& in, array& out) {
   auto [copy_necessary, out_strides] = prepare_reshape(in, out);
   if (copy_necessary) {
     out.set_data(allocator::malloc(out.nbytes()));
-    copy_inplace(in, out, CopyType::General, out.primitive().stream());
+    copy_cpu_inplace(in, out, CopyType::General, out.primitive().stream());
   } else {
     shared_buffer_reshape(in, out_strides, out);
   }
@@ -175,7 +175,7 @@ void AsType::eval_cpu(const std::vector<array>& inputs, array& out) {
   assert(inputs.size() == 1);
   auto& in = inputs[0];
   CopyType ctype = in.flags().contiguous ? CopyType::Vector : CopyType::General;
-  copy(in, out, ctype, stream());
+  copy_cpu(in, out, ctype, stream());
 }
 
 void Concatenate::eval_cpu(const std::vector<array>& inputs, array& out) {
@@ -198,7 +198,7 @@ void Concatenate::eval_cpu(const std::vector<array>& inputs, array& out) {
     size_t data_offset = strides[axis_] * sizes[i];
     out_slice.copy_shared_buffer(
         out, strides, flags, out_slice.size(), data_offset);
-    copy_inplace(inputs[i], out_slice, CopyType::GeneralGeneral, stream());
+    copy_cpu_inplace(inputs[i], out_slice, CopyType::GeneralGeneral, stream());
   }
 }
 
@@ -211,7 +211,7 @@ void Contiguous::eval_cpu(const std::vector<array>& inputs, array& out) {
        (allow_col_major_ && in.flags().col_contiguous))) {
     out.copy_shared_buffer(in);
   } else {
-    copy(in, out, CopyType::General, stream());
+    copy_cpu(in, out, CopyType::General, stream());
   }
 }
 
@@ -235,7 +235,7 @@ void Full::eval_cpu(const std::vector<array>& inputs, array& out) {
   } else {
     ctype = CopyType::General;
   }
-  copy(in, out, ctype, stream());
+  copy_cpu(in, out, ctype, stream());
 }
 
 void Pad::eval_cpu(const std::vector<array>& inputs, array& out) {
@@ -251,7 +251,7 @@ void Pad::eval_cpu(const std::vector<array>& inputs, array& out) {
   assert(val.dtype() == in.dtype() && in.dtype() == out.dtype());
 
   // Fill output with val
-  copy(val, out, CopyType::Scalar, stream());
+  copy_cpu(val, out, CopyType::Scalar, stream());
 
   // Find offset for start of input values
   size_t data_offset = 0;
@@ -266,7 +266,7 @@ void Pad::eval_cpu(const std::vector<array>& inputs, array& out) {
       out, out.strides(), out.flags(), out_slice.size(), data_offset);
 
   // Copy input values into the slice
-  copy_inplace(in, out_slice, CopyType::GeneralGeneral, stream());
+  copy_cpu_inplace(in, out_slice, CopyType::GeneralGeneral, stream());
 }
 
 void RandomBits::eval_cpu(const std::vector<array>& inputs, array& out) {
@@ -340,7 +340,7 @@ void DynamicSlice::eval_cpu(const std::vector<array>& inputs, array& out) {
   out.set_data(allocator::malloc(out.nbytes()));
   auto [in_offset, donated] =
       compute_dynamic_offset(inputs[1], in.strides(), axes_, stream());
-  copy_inplace(
+  copy_cpu_inplace(
       /* const array& src = */ in,
       /* array& dst = */ out,
       /* const Shape& data_shape = */ out.shape(),
@@ -372,11 +372,11 @@ void DynamicSliceUpdate::eval_cpu(
   auto ctype = in.flags().contiguous && in.size() == in.data_size()
       ? CopyType::Vector
       : CopyType::General;
-  copy(in, out, in.data_size() == 1 ? CopyType::Scalar : ctype, stream());
+  copy_cpu(in, out, in.data_size() == 1 ? CopyType::Scalar : ctype, stream());
 
   auto [out_offset, donated] =
       compute_dynamic_offset(inputs[2], out.strides(), axes_, stream());
-  copy_inplace(
+  copy_cpu_inplace(
       /* const array& src = */ upd,
       /* array& dst = */ out,
       /* const std::vector<int>& data_shape = */ upd.shape(),
@@ -412,14 +412,14 @@ void SliceUpdate::eval_cpu(const std::vector<array>& inputs, array& out) {
   auto ctype = in.flags().contiguous && in.size() == in.data_size()
       ? CopyType::Vector
       : CopyType::General;
-  copy(in, out, in.data_size() == 1 ? CopyType::Scalar : ctype, stream());
+  copy_cpu(in, out, in.data_size() == 1 ? CopyType::Scalar : ctype, stream());
 
   // Calculate out strides, initial offset and if copy needs to be made
   auto [data_offset, out_strides] =
       prepare_slice(out, start_indices_, strides_);
 
   // Do copy
-  copy_inplace(
+  copy_cpu_inplace(
       /* const array& src = */ upd,
       /* array& dst = */ out,
       /* const std::vector<int>& data_shape = */ upd.shape(),
@@ -456,9 +456,9 @@ void View::eval_cpu(const std::vector<array>& inputs, array& out) {
     if (in.dtype() == bool_) {
       auto in_tmp = array(in.shape(), uint8, nullptr, {});
       in_tmp.copy_shared_buffer(in);
-      copy_inplace(in_tmp, tmp, CopyType::General, stream());
+      copy_cpu_inplace(in_tmp, tmp, CopyType::General, stream());
     } else {
-      copy_inplace(in, tmp, CopyType::General, stream());
+      copy_cpu_inplace(in, tmp, CopyType::General, stream());
     }
 
     auto flags = out.flags();

mlx/backend/cpu/qrf.cpp

@@ -26,7 +26,7 @@ void qrf_impl(const array& a, array& q, array& r, Stream stream) {
   strides[in.ndim() - 2] = 1;
   strides[in.ndim() - 1] = M;
   in.set_data(allocator::malloc(in.nbytes()), in.nbytes(), strides, flags);
-  copy_inplace(a, in, CopyType::GeneralGeneral, stream);
+  copy_cpu_inplace(a, in, CopyType::GeneralGeneral, stream);
   auto& encoder = cpu::get_command_encoder(stream);
   q.set_data(allocator::malloc(q.nbytes()));
   r.set_data(allocator::malloc(r.nbytes()));

mlx/backend/cpu/quantized.cpp

@@ -529,7 +529,7 @@ void QuantizedMatmul::eval_cpu(const std::vector<array>& inputs, array& out) {
       return arr;
     } else {
       temps.push_back(array(arr.shape(), arr.dtype(), nullptr, {}));
-      copy(arr, temps.back(), CopyType::General, s);
+      copy_cpu(arr, temps.back(), CopyType::General, s);
       return temps.back();
     }
   };
@@ -579,7 +579,7 @@ void GatherQMM::eval_cpu(const std::vector<array>& inputs, array& out) {
       return arr;
     } else {
       temps.push_back(array(arr.shape(), arr.dtype(), nullptr, {}));
-      copy(arr, temps.back(), CopyType::General, s);
+      copy_cpu(arr, temps.back(), CopyType::General, s);
       return temps.back();
     }
   };
@@ -713,7 +713,7 @@ void fast::AffineQuantize::eval_cpu(
       return std::make_pair(arr, false);
     } else {
       array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-      copy(arr, arr_copy, CopyType::General, s);
+      copy_cpu(arr, arr_copy, CopyType::General, s);
       return std::make_pair(arr_copy, true);
     }
   };

mlx/backend/cpu/reduce.cpp

@@ -325,7 +325,15 @@ struct MaxReduce {
   };
 
   template <int N, typename T>
-  T operator()(simd::Simd<T, N> x) {
+  std::enable_if_t<std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    return simd::max(x);
+  };
+
+  template <int N, typename T>
+  std::enable_if_t<!std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    if (simd::any(x != x)) {
+      return static_cast<T>(NAN);
+    }
     return simd::max(x);
   };
 };
@@ -342,7 +350,15 @@ struct MinReduce {
   };
 
   template <int N, typename T>
-  T operator()(simd::Simd<T, N> x) {
+  std::enable_if_t<std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    return simd::min(x);
+  };
+
+  template <int N, typename T>
+  std::enable_if_t<!std::is_integral_v<T>, T> operator()(simd::Simd<T, N> x) {
+    if (simd::any(x != x)) {
+      return static_cast<T>(NAN);
+    }
     return simd::min(x);
   };
 };
@@ -527,10 +543,10 @@ void Reduce::eval_cpu(const std::vector<array>& inputs, array& out) {
             reduce_dispatch_min_max<uint64_t>(in, out, reduce_type_, axes_);
             break;
           case int8:
-            reduce_dispatch_min_max<uint8_t>(in, out, reduce_type_, axes_);
+            reduce_dispatch_min_max<int8_t>(in, out, reduce_type_, axes_);
             break;
           case int16:
-            reduce_dispatch_min_max<uint16_t>(in, out, reduce_type_, axes_);
+            reduce_dispatch_min_max<int16_t>(in, out, reduce_type_, axes_);
             break;
           case int32:
             reduce_dispatch_min_max<int32_t>(in, out, reduce_type_, axes_);

mlx/backend/cpu/scan.cpp

@@ -251,7 +251,7 @@ void Scan::eval_cpu(const std::vector<array>& inputs, array& out) {
   auto in = inputs[0];
   if (!in.flags().row_contiguous) {
     array arr_copy(in.shape(), in.dtype(), nullptr, {});
-    copy(in, arr_copy, CopyType::General, stream());
+    copy_cpu(in, arr_copy, CopyType::General, stream());
     in = arr_copy;
     encoder.add_temporary(arr_copy);
   }

mlx/backend/cpu/softmax.cpp

@@ -132,7 +132,7 @@ void Softmax::eval_cpu(const std::vector<array>& inputs, array& out) {
       return x;
     } else {
       array x_copy(x.shape(), x.dtype(), nullptr, {});
-      copy(x, x_copy, CopyType::General, s);
+      copy_cpu(x, x_copy, CopyType::General, s);
       out.copy_shared_buffer(x_copy);
       return x_copy;
     }

mlx/backend/cpu/sort.cpp

@@ -334,8 +334,10 @@ void Sort::eval_cpu(const std::vector<array>& inputs, array& out) {
   auto& in = inputs[0];
 
   // Copy input to output
-  CopyType ctype = in.flags().contiguous ? CopyType::Vector : CopyType::General;
-  copy(in, out, ctype, stream());
+  CopyType ctype = (in.flags().contiguous && in.strides()[axis_] != 0)
+      ? CopyType::Vector
+      : CopyType::General;
+  copy_cpu(in, out, ctype, stream());
 
   auto& encoder = cpu::get_command_encoder(stream());
   encoder.set_output_array(out);
@@ -426,8 +428,10 @@ void Partition::eval_cpu(const std::vector<array>& inputs, array& out) {
   auto& in = inputs[0];
 
   // Copy input to output
-  CopyType ctype = in.flags().contiguous ? CopyType::Vector : CopyType::General;
-  copy(in, out, ctype, stream());
+  CopyType ctype = (in.flags().contiguous && in.strides()[axis_] != 0)
+      ? CopyType::Vector
+      : CopyType::General;
+  copy_cpu(in, out, ctype, stream());
 
   auto& encoder = cpu::get_command_encoder(stream());
   encoder.set_output_array(out);

mlx/backend/cpu/svd.cpp

@@ -31,7 +31,7 @@ void svd_impl(
 
   // lapack clobbers the input, so we have to make a copy.
   array in(a.shape(), a.dtype(), nullptr, {});
-  copy(
+  copy_cpu(
       a,
       in,
       a.flags().row_contiguous ? CopyType::Vector : CopyType::General,

mlx/backend/cuda/CMakeLists.txt

@@ -35,12 +35,16 @@ target_sources(
           ${CMAKE_CURRENT_SOURCE_DIR}/reduce/row_reduce.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/rms_norm.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/rope.cu
+          ${CMAKE_CURRENT_SOURCE_DIR}/scan.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/slicing.cpp
           ${CMAKE_CURRENT_SOURCE_DIR}/softmax.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/sort.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/ternary.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/unary.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/utils.cpp
+          ${CMAKE_CURRENT_SOURCE_DIR}/quantized/affine_quantize.cu
+          ${CMAKE_CURRENT_SOURCE_DIR}/quantized/qmm.cu
+          ${CMAKE_CURRENT_SOURCE_DIR}/quantized/quantized.cu
           ${CMAKE_CURRENT_SOURCE_DIR}/worker.cpp)
 
 target_compile_definitions(mlx PRIVATE MLX_USE_CUDA)
@@ -67,6 +71,11 @@ target_include_directories(mlx PRIVATE "${CMAKE_CURRENT_BINARY_DIR}/gen")
 target_compile_options(mlx
                        PRIVATE "$<$<COMPILE_LANGUAGE:CUDA>:--extended-lambda>")
 
+# Enable calling host constexpr functions from device. This is needed because
+# the constexpr version of isnan is host only.
+target_compile_options(
+  mlx PRIVATE "$<$<COMPILE_LANGUAGE:CUDA>:--expt-relaxed-constexpr>")
+
 # CUDA 12.8 emits warning #20280-D for copy kernels which is a false positive.
 # Explicitly pass this flag to suppress the warning, it is safe to set it to
 # true but the warning wouldn't be suppressed.
@@ -83,7 +92,7 @@ target_compile_options(
 # Compute capability 7 is required for synchronization between CPU/GPU with
 # managed memory. TODO: Add more architectures for potential performance gain.
 set(MLX_CUDA_ARCHITECTURES
-    "70;80"
+    "80"
     CACHE STRING "CUDA architectures")
 message(STATUS "CUDA architectures: ${MLX_CUDA_ARCHITECTURES}")
 set_target_properties(mlx PROPERTIES CUDA_ARCHITECTURES
@@ -119,3 +128,16 @@ target_link_libraries(mlx PRIVATE CUDA::nvrtc CUDA::cuda_driver)
 # Suppress nvcc warnings on MLX headers.
 target_compile_options(mlx PRIVATE $<$<COMPILE_LANGUAGE:CUDA>:-Xcudafe
                                    --diag_suppress=997>)
+
+# Install CCCL headers for JIT.
+install(DIRECTORY ${cccl_SOURCE_DIR}/include/cuda
+        DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/cccl)
+
+# Make Thunderkittens available
+FetchContent_Declare(
+  kittens
+  GIT_REPOSITORY https://github.com/HazyResearch/ThunderKittens.git
+  GIT_TAG aaab847f430ed313ed466e64b25b9177babd1db8
+  GIT_SHALLOW TRUE)
+FetchContent_MakeAvailable(kittens)
+target_include_directories(mlx BEFORE PRIVATE "${kittens_SOURCE_DIR}/include")

mlx/backend/cuda/allocator.cpp

@@ -17,6 +17,52 @@ namespace cu {
 
 constexpr int page_size = 16384;
 
+// Any allocations smaller than this will try to use the small pool
+constexpr int small_block_size = 8;
+
+// The small pool size in bytes. This should be a multiple of the host page
+// size and small_block_size.
+constexpr int small_pool_size = 4 * page_size;
+
+SmallSizePool::SmallSizePool() {
+  CHECK_CUDA_ERROR(cudaMallocManaged(&buffer_, small_pool_size));
+  end_ = reinterpret_cast<void*>(
+      reinterpret_cast<char*>(buffer_) + small_pool_size);
+  next_free_ = reinterpret_cast<Block*>(buffer_);
+
+  auto num_blocks = small_pool_size / small_block_size;
+  auto curr = next_free_;
+  for (size_t i = 0; i < num_blocks - 1; ++i) {
+    curr->next = reinterpret_cast<Block*>(
+        reinterpret_cast<char*>(buffer_) + (i + 1) * small_block_size);
+    curr = curr->next;
+  }
+  curr->next = nullptr;
+}
+
+SmallSizePool::~SmallSizePool() {
+  CHECK_CUDA_ERROR(cudaFree(buffer_));
+}
+
+void* SmallSizePool::malloc() {
+  if (next_free_ == nullptr) {
+    return nullptr;
+  }
+  Block* b = next_free_;
+  next_free_ = next_free_->next;
+  return static_cast<void*>(b);
+}
+
+void SmallSizePool::free(void* p) {
+  auto b = static_cast<Block*>(p);
+  b->next = next_free_;
+  next_free_ = b;
+}
+
+bool SmallSizePool::in_pool(void* p) {
+  return (p >= buffer_) && (p < end_);
+}
+
 CudaAllocator::CudaAllocator()
     : buffer_cache_(
           page_size,
@@ -36,7 +82,9 @@ Buffer CudaAllocator::malloc(size_t size) {
   // Find available buffer from cache.
   auto orig_size = size;
   std::unique_lock lock(mutex_);
-  if (size < page_size) {
+  if (size <= small_block_size) {
+    size = 8;
+  } else if (size < page_size) {
     size = next_power_of_2(size);
   } else {
     size = page_size * ((size + page_size - 1) / page_size);
@@ -53,11 +101,19 @@ Buffer CudaAllocator::malloc(size_t size) {
 
     lock.unlock();
     buf = new CudaBuffer{nullptr, size};
+
+    // Try the scalar pool first
+    if (size <= small_block_size) {
+      buf->data = scalar_pool_.malloc();
+    }
+    if (!buf->data) {
       cudaError_t err = cudaMallocManaged(&buf->data, size);
       if (err != cudaSuccess && err != cudaErrorMemoryAllocation) {
         throw std::runtime_error(fmt::format(
             "cudaMallocManaged failed: {}.", cudaGetErrorString(err)));
       }
+    }
+
     lock.lock();
   }
   active_memory_ += size;
@@ -116,7 +172,11 @@ void CudaAllocator::cuda_free(void* buf) {
       return;
     }
   }
+  if (scalar_pool_.in_pool(buf)) {
+    scalar_pool_.free(buf);
+  } else {
     cudaFree(buf);
+  }
 }
 
 size_t CudaAllocator::get_active_memory() const {

mlx/backend/cuda/allocator.h

@@ -22,6 +22,28 @@ struct CudaBuffer {
   size_t size;
 };
 
+class SmallSizePool {
+ private:
+  struct Block {
+    Block* next;
+  };
+
+  void* buffer_{nullptr};
+  Block* next_free_{nullptr};
+  void* end_{nullptr};
+
+ public:
+  SmallSizePool();
+  ~SmallSizePool();
+
+  SmallSizePool(const SmallSizePool&) = delete;
+  SmallSizePool& operator=(const SmallSizePool&) = delete;
+
+  void* malloc();
+  void free(void* p);
+  bool in_pool(void* p);
+};
+
 class CudaAllocator : public allocator::Allocator {
  public:
   Buffer malloc(size_t size) override;
@@ -60,6 +82,7 @@ class CudaAllocator : public allocator::Allocator {
   BufferCache<CudaBuffer> buffer_cache_;
   size_t active_memory_{0};
   size_t peak_memory_{0};
+  SmallSizePool scalar_pool_;
 };
 
 CudaAllocator& allocator();

mlx/backend/cuda/arg_reduce.cu

@@ -1,6 +1,7 @@
 // Copyright © 2025 Apple Inc.
 #include "mlx/backend/common/utils.h"
 #include "mlx/backend/cuda/device.h"
+#include "mlx/backend/cuda/device/fp16_math.cuh"
 #include "mlx/backend/cuda/iterators/strided_iterator.cuh"
 #include "mlx/backend/cuda/kernel_utils.cuh"
 #include "mlx/dtype_utils.h"
@@ -165,6 +166,7 @@ void ArgReduce::eval_gpu(const std::vector<array>& inputs, array& out) {
           kernel,
           num_blocks,
           block_dim(),
+          0,
           in.data<T>(),
           out.data<uint32_t>(),
           out.size(),

mlx/backend/cuda/binary.cu

@@ -3,7 +3,6 @@
 #include "mlx/backend/common/binary.h"
 #include "mlx/backend/cuda/device.h"
 #include "mlx/backend/cuda/device/binary_ops.cuh"
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
 #include "mlx/backend/cuda/kernel_utils.cuh"
 #include "mlx/dtype_utils.h"
 #include "mlx/primitives.h"
@@ -17,35 +16,86 @@ namespace cu {
 
 namespace cg = cooperative_groups;
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void binary_ss(const In* a, const In* b, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(a[0], b[0]);
+
+  if ((index + 1) * N_READS > size) {
+    for (int i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(a[0], b[0]);
+    }
+  } else {
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(a[0], b[0]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void binary_sv(const In* a, const In* b, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(a[0], b[index]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(a[0], b[i]);
+    }
+  } else {
+    auto b_vec = load_vector<N_READS>(b, index);
+
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(a[0], b_vec.val[i]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void binary_vs(const In* a, const In* b, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(a[index], b[0]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(a[i], b[0]);
+    }
+  } else {
+    auto a_vec = load_vector<N_READS>(a, index);
+
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(a_vec.val[i], b[0]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void binary_vv(const In* a, const In* b, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(a[index], b[index]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(a[i], b[i]);
+    }
+  } else {
+    auto a_vec = load_vector<N_READS>(a, index);
+    auto b_vec = load_vector<N_READS>(b, index);
+
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(a_vec.val[i], b_vec.val[i]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
@@ -126,7 +176,7 @@ template <typename Op>
 void binary_op_gpu_inplace(
     const std::vector<array>& inputs,
     array& out,
-    std::string_view op,
+    const char* op,
     const Stream& s) {
   assert(inputs.size() > 1);
   const auto& a = inputs[0];
@@ -169,6 +219,7 @@ void binary_op_gpu_inplace(
                         kernel,
                         num_blocks,
                         block_dims,
+                        0,
                         a.data<InType>(),
                         b.data<InType>(),
                         out.data<OutType>(),
@@ -185,6 +236,7 @@ void binary_op_gpu_inplace(
                       kernel,
                       num_blocks,
                       block_dims,
+                      0,
                       a.data<InType>(),
                       b.data<InType>(),
                       out.data<OutType>(),
@@ -196,22 +248,30 @@ void binary_op_gpu_inplace(
                 }
               });
         } else {
-          dispatch_bool(out.data_size() > INT32_MAX, [&](auto large) {
+          dispatch_bool(out.data_size() > UINT32_MAX, [&](auto large) {
             using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
-            auto kernel = cu::binary_ss<Op, InType, OutType, IdxT>;
+            // TODO: Choose optimized value based on type size.
+            constexpr int N_READS = 4;
+            auto kernel = cu::binary_ss<Op, InType, OutType, IdxT, N_READS>;
             if (bopt == BinaryOpType::ScalarVector) {
-              kernel = cu::binary_sv<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_sv<Op, InType, OutType, IdxT, N_READS>;
             } else if (bopt == BinaryOpType::VectorScalar) {
-              kernel = cu::binary_vs<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_vs<Op, InType, OutType, IdxT, N_READS>;
             } else if (bopt == BinaryOpType::VectorVector) {
-              kernel = cu::binary_vv<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_vv<Op, InType, OutType, IdxT, N_READS>;
             }
             auto [num_blocks, block_dims] = get_launch_args(
-                kernel, out.data_size(), out.shape(), out.strides(), large());
+                kernel,
+                out.data_size(),
+                out.shape(),
+                out.strides(),
+                large(),
+                N_READS);
             encoder.add_kernel_node(
                 kernel,
                 num_blocks,
                 block_dims,
+                0,
                 a.data<InType>(),
                 b.data<InType>(),
                 out.data<OutType>(),
@@ -233,7 +293,7 @@ template <typename Op>
 void binary_op_gpu(
     const std::vector<array>& inputs,
     array& out,
-    std::string_view op,
+    const char* op,
     const Stream& s) {
   auto& a = inputs[0];
   auto& b = inputs[1];
@@ -246,7 +306,7 @@ void binary_op_gpu(
   void func::eval_gpu(const std::vector<array>& inputs, array& out) { \
     nvtx3::scoped_range r(#func "::eval_gpu");                        \
     auto& s = out.primitive().stream();                               \
-    binary_op_gpu<cu::func>(inputs, out, get_primitive_string(this), s); \
+    binary_op_gpu<cu::func>(inputs, out, name(), s);                  \
   }
 
 BINARY_GPU(Add)
@@ -270,33 +330,31 @@ BINARY_GPU(Subtract)
 void Equal::eval_gpu(const std::vector<array>& inputs, array& out) {
   nvtx3::scoped_range r("Equal::eval_gpu");
   auto& s = out.primitive().stream();
-  auto op = get_primitive_string(this);
   if (equal_nan_) {
-    binary_op_gpu<cu::NaNEqual>(inputs, out, op, s);
+    binary_op_gpu<cu::NaNEqual>(inputs, out, name(), s);
   } else {
-    binary_op_gpu<cu::Equal>(inputs, out, op, s);
+    binary_op_gpu<cu::Equal>(inputs, out, name(), s);
   }
 }
 
 void BitwiseBinary::eval_gpu(const std::vector<array>& inputs, array& out) {
   nvtx3::scoped_range r("BitwiseBinary::eval_gpu");
   auto& s = out.primitive().stream();
-  auto op = get_primitive_string(this);
   switch (op_) {
     case BitwiseBinary::And:
-      binary_op_gpu<cu::BitwiseAnd>(inputs, out, op, s);
+      binary_op_gpu<cu::BitwiseAnd>(inputs, out, name(), s);
       break;
     case BitwiseBinary::Or:
-      binary_op_gpu<cu::BitwiseOr>(inputs, out, op, s);
+      binary_op_gpu<cu::BitwiseOr>(inputs, out, name(), s);
       break;
     case BitwiseBinary::Xor:
-      binary_op_gpu<cu::BitwiseXor>(inputs, out, op, s);
+      binary_op_gpu<cu::BitwiseXor>(inputs, out, name(), s);
       break;
     case BitwiseBinary::LeftShift:
-      binary_op_gpu<cu::LeftShift>(inputs, out, op, s);
+      binary_op_gpu<cu::LeftShift>(inputs, out, name(), s);
       break;
     case BitwiseBinary::RightShift:
-      binary_op_gpu<cu::RightShift>(inputs, out, op, s);
+      binary_op_gpu<cu::RightShift>(inputs, out, name(), s);
       break;
   }
 }

mlx/backend/cuda/binary_two.cu

@@ -3,7 +3,6 @@
 #include "mlx/backend/common/binary.h"
 #include "mlx/backend/cuda/device.h"
 #include "mlx/backend/cuda/device/binary_ops.cuh"
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
 #include "mlx/backend/cuda/kernel_utils.cuh"
 #include "mlx/dtype_utils.h"
 #include "mlx/primitives.h"
@@ -17,52 +16,119 @@ namespace cu {
 
 namespace cg = cooperative_groups;
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void
-binary_ss(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
+binary_two_ss(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
       auto out = Op{}(a[0], b[0]);
-    out_a[0] = out[0];
-    out_b[0] = out[1];
+      out_a[i] = out[0];
+      out_b[i] = out[1];
+    }
+  } else {
+    AlignedVector<Out, N_READS> out_a_vec;
+    AlignedVector<Out, N_READS> out_b_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      auto out = Op{}(a[0], b[0]);
+      out_a_vec.val[i] = out[0];
+      out_b_vec.val[i] = out[1];
+    }
+
+    store_vector<N_READS>(out_a, index, out_a_vec);
+    store_vector<N_READS>(out_b, index, out_b_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void
-binary_sv(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
+binary_two_sv(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    auto out = Op{}(a[0], b[index]);
-    out_a[index] = out[0];
-    out_b[index] = out[1];
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      auto out = Op{}(a[0], b[i]);
+      out_a[i] = out[0];
+      out_b[i] = out[1];
+    }
+  } else {
+    auto b_vec = load_vector<N_READS>(b, index);
+
+    AlignedVector<Out, N_READS> out_a_vec;
+    AlignedVector<Out, N_READS> out_b_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      auto out = Op{}(a[0], b_vec.val[i]);
+      out_a_vec.val[i] = out[0];
+      out_b_vec.val[i] = out[1];
+    }
+
+    store_vector<N_READS>(out_a, index, out_a_vec);
+    store_vector<N_READS>(out_b, index, out_b_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void
-binary_vs(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
+binary_two_vs(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    auto out = Op{}(a[index], b[0]);
-    out_a[index] = out[0];
-    out_b[index] = out[1];
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      auto out = Op{}(a[i], b[0]);
+      out_a[i] = out[0];
+      out_b[i] = out[1];
+    }
+  } else {
+    auto a_vec = load_vector<N_READS>(a, index);
+
+    AlignedVector<Out, N_READS> out_a_vec;
+    AlignedVector<Out, N_READS> out_b_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      auto out = Op{}(a_vec.val[i], b[0]);
+      out_a_vec.val[i] = out[0];
+      out_b_vec.val[i] = out[1];
+    }
+
+    store_vector<N_READS>(out_a, index, out_a_vec);
+    store_vector<N_READS>(out_b, index, out_b_vec);
   }
 }
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void
-binary_vv(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
+binary_two_vv(const In* a, const In* b, Out* out_a, Out* out_b, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    auto out = Op{}(a[index], b[index]);
-    out_a[index] = out[0];
-    out_b[index] = out[1];
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      auto out = Op{}(a[i], b[i]);
+      out_a[i] = out[0];
+      out_b[i] = out[1];
+    }
+  } else {
+    auto a_vec = load_vector<N_READS>(a, index);
+    auto b_vec = load_vector<N_READS>(b, index);
+
+    AlignedVector<Out, N_READS> out_a_vec;
+    AlignedVector<Out, N_READS> out_b_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      auto out = Op{}(a_vec.val[i], b_vec.val[i]);
+      out_a_vec.val[i] = out[0];
+      out_b_vec.val[i] = out[1];
+    }
+
+    store_vector<N_READS>(out_a, index, out_a_vec);
+    store_vector<N_READS>(out_b, index, out_b_vec);
   }
 }
 
 template <typename Op, typename In, typename Out, typename IdxT, int NDIM>
-__global__ void binary_g_nd(
+__global__ void binary_two_g_nd(
     const In* a,
     const In* b,
     Out* out_a,
@@ -82,7 +148,7 @@ __global__ void binary_g_nd(
 }
 
 template <typename Op, typename In, typename Out, typename IdxT>
-__global__ void binary_g(
+__global__ void binary_two_g(
     const In* a,
     const In* b,
     Out* out_a,
@@ -103,7 +169,7 @@ __global__ void binary_g(
 }
 
 template <typename Op, typename In, typename Out>
-constexpr bool supports_binary_op() {
+constexpr bool supports_binary_two_op() {
   if (std::is_same_v<Op, DivMod>) {
     return std::is_same_v<In, Out> &&
         (std::is_integral_v<Out> || is_floating_v<Out>);
@@ -114,10 +180,10 @@ constexpr bool supports_binary_op() {
 } // namespace cu
 
 template <typename Op>
-void binary_op_gpu_inplace(
+void binary_two_op_gpu_inplace(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    std::string_view op,
+    const char* op,
     const Stream& s) {
   assert(inputs.size() > 1);
   const auto& a = inputs[0];
@@ -141,7 +207,7 @@ void binary_op_gpu_inplace(
     dispatch_all_types(out_a.dtype(), [&](auto out_type_tag) {
       using CTYPE_IN = MLX_GET_TYPE(in_type_tag);
       using CTYPE_OUT = MLX_GET_TYPE(out_type_tag);
-      if constexpr (cu::supports_binary_op<Op, CTYPE_IN, CTYPE_OUT>()) {
+      if constexpr (cu::supports_binary_two_op<Op, CTYPE_IN, CTYPE_OUT>()) {
         using InType = cuda_type_t<CTYPE_IN>;
         using OutType = cuda_type_t<CTYPE_OUT>;
 
@@ -161,14 +227,19 @@ void binary_op_gpu_inplace(
                 int ndim = shape.size();
                 if (ndim <= 3) {
                   dispatch_1_2_3(ndim, [&](auto dims_constant) {
-                    auto kernel = cu::
-                        binary_g_nd<Op, InType, OutType, IdxT, dims_constant()>;
+                    auto kernel = cu::binary_two_g_nd<
+                        Op,
+                        InType,
+                        OutType,
+                        IdxT,
+                        dims_constant()>;
                     auto [num_blocks, block_dims] =
                         get_launch_args(kernel, out_a, large());
                     encoder.add_kernel_node(
                         kernel,
                         num_blocks,
                         block_dims,
+                        0,
                         a.data<InType>(),
                         b.data<InType>(),
                         out_a.data<OutType>(),
@@ -179,13 +250,14 @@ void binary_op_gpu_inplace(
                         const_param<dims_constant()>(b_strides));
                   });
                 } else {
-                  auto kernel = cu::binary_g<Op, InType, OutType, IdxT>;
+                  auto kernel = cu::binary_two_g<Op, InType, OutType, IdxT>;
                   auto [num_blocks, block_dims] =
                       get_launch_args(kernel, out_a, large());
                   encoder.add_kernel_node(
                       kernel,
                       num_blocks,
                       block_dims,
+                      0,
                       a.data<InType>(),
                       b.data<InType>(),
                       out_a.data<OutType>(),
@@ -198,26 +270,30 @@ void binary_op_gpu_inplace(
                 }
               });
         } else {
-          dispatch_bool(out_a.data_size() > INT32_MAX, [&](auto large) {
+          dispatch_bool(out_a.data_size() > UINT32_MAX, [&](auto large) {
             using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
-            auto kernel = cu::binary_ss<Op, InType, OutType, IdxT>;
+            // TODO: Choose optimized value based on type size.
+            constexpr int N_READS = 4;
+            auto kernel = cu::binary_two_ss<Op, InType, OutType, IdxT, N_READS>;
             if (bopt == BinaryOpType::ScalarVector) {
-              kernel = cu::binary_sv<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_two_sv<Op, InType, OutType, IdxT, N_READS>;
             } else if (bopt == BinaryOpType::VectorScalar) {
-              kernel = cu::binary_vs<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_two_vs<Op, InType, OutType, IdxT, N_READS>;
             } else if (bopt == BinaryOpType::VectorVector) {
-              kernel = cu::binary_vv<Op, InType, OutType, IdxT>;
+              kernel = cu::binary_two_vv<Op, InType, OutType, IdxT, N_READS>;
             }
             auto [num_blocks, block_dims] = get_launch_args(
                 kernel,
                 out_a.data_size(),
                 out_a.shape(),
                 out_a.strides(),
-                large());
+                large(),
+                N_READS);
             encoder.add_kernel_node(
                 kernel,
                 num_blocks,
                 block_dims,
+                0,
                 a.data<InType>(),
                 b.data<InType>(),
                 out_a.data<OutType>(),
@@ -237,17 +313,17 @@ void binary_op_gpu_inplace(
 }
 
 template <typename Op>
-void binary_op_gpu(
+void binary_two_op_gpu(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    std::string_view op,
+    const char* op,
     const Stream& s) {
   auto& a = inputs[0];
   auto& b = inputs[1];
   auto bopt = get_binary_op_type(a, b);
   set_binary_op_output_data(a, b, outputs[0], bopt);
   set_binary_op_output_data(a, b, outputs[1], bopt);
-  binary_op_gpu_inplace<Op>(inputs, outputs, op, s);
+  binary_two_op_gpu_inplace<Op>(inputs, outputs, op, s);
 }
 
 void DivMod::eval_gpu(
@@ -255,7 +331,7 @@ void DivMod::eval_gpu(
     std::vector<array>& outputs) {
   nvtx3::scoped_range r("DivMod::eval_gpu");
   auto& s = outputs[0].primitive().stream();
-  binary_op_gpu<cu::DivMod>(inputs, outputs, get_primitive_string(this), s);
+  binary_two_op_gpu<cu::DivMod>(inputs, outputs, name(), s);
 }
 
 } // namespace mlx::core

mlx/backend/cuda/compiled.cpp

@@ -53,9 +53,10 @@ struct FusedKernelBuilder {
 
     // Build function signature.
     if (contiguous) {
-      os += "template <typename IdxT = uint32_t>\n";
+      os += "template <typename IdxT = uint32_t, int work_per_thread = 1>\n";
     } else {
-      os += "template <int NDIM, typename IdxT = uint32_t>\n";
+      os +=
+          "template <int NDIM, typename IdxT = uint32_t, int work_per_thread = 1>\n";
     }
     os += fmt::format("__global__ void {}(\n", kernel_name + name);
     for (size_t i = 0; i < params.size(); ++i) {
@@ -67,12 +68,46 @@ struct FusedKernelBuilder {
     }
     os += ") {\n";
 
-    // Index.
+    // Index. For non contiguous kernels we create a separate index
+    // variable per variable otherwise everyone uses `index`.
     os +=
-        "  IdxT index = cg::this_grid().thread_rank();\n"
+        "  IdxT index = cg::this_grid().thread_rank() * work_per_thread;\n"
         "  if (index >= size) {\n"
         "    return;\n"
         "  }\n";
+    if (!contiguous) {
+      for (size_t i = 0; i < inputs.size(); ++i) {
+        const auto& x = inputs[i];
+        const std::string& xname = namer.get_name(x);
+        if (is_scalar(x) || is_constant(i)) {
+          continue;
+        }
+        os += "  IdxT " + xname + "_idx = 0;\n";
+      }
+      os += "  {\n";
+      os += "    IdxT loc = index;\n";
+      os +=
+          "    #pragma unroll\n"
+          "    for (int i = NDIM - 1; i >= 0; i--) {\n";
+      for (size_t i = 0; i < inputs.size(); ++i) {
+        const auto& x = inputs[i];
+        const std::string& xname = namer.get_name(x);
+        if (is_scalar(x) || is_constant(i)) {
+          continue;
+        }
+        os += "      " + xname + "_idx += (loc \% shape[i]) * IdxT(" + xname +
+            "_strides[i]);\n";
+      }
+      os +=
+          "      loc /= shape[i];\n"
+          "    }\n"
+          "  }\n";
+    }
+
+    // Work loop
+    os +=
+        "\n"
+        "  for (int i = 0; i < work_per_thread && index < size; i++) {\n";
 
     // Read inputs.
     for (size_t i = 0; i < inputs.size(); ++i) {
@@ -89,10 +124,7 @@ struct FusedKernelBuilder {
       } else if (contiguous) {
         value = fmt::format("{}[index]", xname);
       } else {
-        std::string index = fmt::format(
-            "elem_to_loc_nd<NDIM>(index, shape.data(), {}_strides.data())",
-            xname);
-        value = fmt::format("{}[{}]", xname, index);
+        value = fmt::format("{}[{}_idx]", xname, xname);
       }
       os += fmt::format("    {} tmp_{} = {};\n", type, xname, value);
     }
@@ -106,9 +138,7 @@ struct FusedKernelBuilder {
         value = fmt::format(
             "static_cast<{}>(tmp_{})", type, namer.get_name(x.inputs()[0]));
       } else {
-        std::ostringstream ss;
-        x.primitive().print(ss);
-        value = ss.str();
+        value = x.primitive().name();
         value += "{}(";
         for (size_t i = 0; i < x.inputs().size() - 1; ++i) {
           value += fmt::format("tmp_{}, ", namer.get_name(x.inputs()[i]));
@@ -123,6 +153,22 @@ struct FusedKernelBuilder {
       os += fmt::format("    {0}[index] = tmp_{0};\n", namer.get_name(x));
     }
 
+    // End of work loop
+    os +=
+        "\n"
+        "    index++;\n";
+    if (!contiguous) {
+      for (size_t i = 0; i < inputs.size(); ++i) {
+        const auto& x = inputs[i];
+        const std::string& xname = namer.get_name(x);
+        if (is_scalar(x) || is_constant(i)) {
+          continue;
+        }
+        os += "    " + xname + "_idx += " + xname + "_strides[NDIM - 1];\n";
+      }
+    }
+    os += "  }\n";
+
     os += "}\n";
   }
 };
@@ -158,15 +204,28 @@ void Compiled::eval_gpu(
     builder.build("_strided", false);
     builder.os += "\n} // namespace mlx::core::cu\n";
     // Build kernel names.
-    std::vector<std::string> kernel_names = {
-        fmt::format("mlx::core::cu::{}_contiguous<uint32_t>", lib_name()),
-        fmt::format("mlx::core::cu::{}_contiguous<int64_t>", lib_name()),
-    };
+    std::vector<std::string> kernel_names;
+    for (auto work_per_thread : std::array<int, 2>{1, 4}) {
+      kernel_names.push_back(fmt::format(
+          "mlx::core::cu::{}_contiguous<uint32_t, {}>",
+          lib_name(),
+          work_per_thread));
+      kernel_names.push_back(fmt::format(
+          "mlx::core::cu::{}_contiguous<int64_t, {}>",
+          lib_name(),
+          work_per_thread));
       for (int i = 1; i <= MAX_NDIM; ++i) {
         kernel_names.push_back(fmt::format(
-          "mlx::core::cu::{}_strided<{}, uint32_t>", lib_name(), i));
-      kernel_names.push_back(
-          fmt::format("mlx::core::cu::{}_strided<{}, int64_t>", lib_name(), i));
+            "mlx::core::cu::{}_strided<{}, uint32_t, {}>",
+            lib_name(),
+            i,
+            work_per_thread));
+        kernel_names.push_back(fmt::format(
+            "mlx::core::cu::{}_strided<{}, int64_t, {}>",
+            lib_name(),
+            i,
+            work_per_thread));
+      }
     }
     return std::make_pair(std::move(builder.os), std::move(kernel_names));
   });
@@ -209,13 +268,21 @@ void Compiled::eval_gpu(
     args.append<uint32_t>(outputs[0].data_size());
   }
 
+  // Choose work per thread
+  int work_per_thread = 4;
+  if (!contiguous && shape.back() % work_per_thread != 0) {
+    work_per_thread = 1;
+  }
+
   // Launch kernel.
   const char* index_type = large ? "int64_t" : "uint32_t";
   std::string kernel_name = fmt::format("mlx::core::cu::{}", lib_name());
   if (contiguous) {
-    kernel_name += fmt::format("_contiguous<{}>", index_type);
+    kernel_name +=
+        fmt::format("_contiguous<{}, {}>", index_type, work_per_thread);
   } else {
-    kernel_name += fmt::format("_strided<{}, {}>", shape.size(), index_type);
+    kernel_name += fmt::format(
+        "_strided<{}, {}, {}>", shape.size(), index_type, work_per_thread);
   }
   auto& encoder = cu::get_command_encoder(s);
   for (const auto& in : inputs) {
@@ -226,8 +293,9 @@ void Compiled::eval_gpu(
   }
 
   auto kernel = mod.get_kernel(kernel_name);
-  auto [num_blocks, block_dims] = get_launch_args(kernel, outputs[0], large);
-  encoder.add_kernel_node(kernel, num_blocks, block_dims, args.args());
+  auto [num_blocks, block_dims] =
+      get_launch_args(kernel, outputs[0], large, work_per_thread);
+  encoder.add_kernel_node(kernel, num_blocks, block_dims, 0, args.args());
 }
 
 } // namespace mlx::core

mlx/backend/cuda/copy/copy_contiguous.cu

@@ -10,19 +10,43 @@ namespace cu {
 
 namespace cg = cooperative_groups;
 
-template <typename In, typename Out, typename IdxT>
+template <typename In, typename Out, typename IdxT, int N_READS>
 __global__ void copy_s(const In* in, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = CastOp<In, Out>{}(in[0]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = cast_to<Out>(in[0]);
+    }
+  } else {
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = cast_to<Out>(in[0]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
-template <typename In, typename Out, typename IdxT>
+template <typename In, typename Out, typename IdxT, int N_READS>
 __global__ void copy_v(const In* in, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = CastOp<In, Out>{}(in[index]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = cast_to<Out>(in[i]);
+    }
+  } else {
+    auto in_vec = load_vector<N_READS>(in, index);
+
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = cast_to<Out>(in_vec.val[i]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
@@ -41,16 +65,24 @@ void copy_contiguous(
         using InType = cuda_type_t<MLX_GET_TYPE(in_type_tag)>;
         using OutType = cuda_type_t<MLX_GET_TYPE(out_type_tag)>;
         using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
-        auto kernel = cu::copy_s<InType, OutType, IdxT>;
+        // TODO: Choose optimized value based on type size.
+        constexpr int N_READS = 4;
+        auto kernel = cu::copy_s<InType, OutType, IdxT, N_READS>;
         if (ctype == CopyType::Vector) {
-          kernel = cu::copy_v<InType, OutType, IdxT>;
+          kernel = cu::copy_v<InType, OutType, IdxT, N_READS>;
         }
         auto [num_blocks, block_dims] = get_launch_args(
-            kernel, out.data_size(), out.shape(), out.strides(), large());
+            kernel,
+            out.data_size(),
+            out.shape(),
+            out.strides(),
+            large(),
+            N_READS);
         encoder.add_kernel_node(
             kernel,
             num_blocks,
             block_dims,
+            0,
             in.data<InType>() + in_offset,
             out.data<OutType>() + out_offset,
             out.data_size());

mlx/backend/cuda/copy/copy_general.cu

@@ -79,6 +79,7 @@ void copy_general(
                     kernel,
                     num_blocks,
                     block_dims,
+                    0,
                     in_ptr,
                     out_ptr,
                     data_size,
@@ -94,6 +95,7 @@ void copy_general(
                   kernel,
                   num_blocks,
                   block_dims,
+                  0,
                   in_ptr,
                   out_ptr,
                   data_size,

mlx/backend/cuda/copy/copy_general_dynamic.cu

@@ -82,6 +82,7 @@ void copy_general_dynamic(
                     kernel,
                     num_blocks,
                     block_dims,
+                    0,
                     in_ptr,
                     out_ptr,
                     out.size(),
@@ -99,6 +100,7 @@ void copy_general_dynamic(
                   kernel,
                   num_blocks,
                   block_dims,
+                  0,
                   in_ptr,
                   out_ptr,
                   out.size(),

mlx/backend/cuda/copy/copy_general_input.cu

@@ -71,6 +71,7 @@ void copy_general_input(
                     kernel,
                     num_blocks,
                     block_dims,
+                    0,
                     in_ptr,
                     out_ptr,
                     out.size(),
@@ -85,6 +86,7 @@ void copy_general_input(
                   kernel,
                   num_blocks,
                   block_dims,
+                  0,
                   in_ptr,
                   out_ptr,
                   out.size(),

mlx/backend/cuda/device.cpp

@@ -57,8 +57,15 @@ void Device::make_current() {
   }
 }
 
+CommandEncoder& Device::get_command_encoder(Stream s) {
+  auto it = encoders_.find(s.index);
+  if (it == encoders_.end()) {
+    it = encoders_.try_emplace(s.index, *this).first;
+  }
+  return it->second;
+}
+
 CommandEncoder::CaptureContext::CaptureContext(CommandEncoder& enc) : enc(enc) {
-  CHECK_CUDA_ERROR(cudaGraphCreate(&graph, 0));
   CHECK_CUDA_ERROR(
       cudaStreamBeginCapture(enc.stream(), cudaStreamCaptureModeGlobal));
 }
@@ -168,15 +175,7 @@ void CommandEncoder::insert_graph_dependencies(std::vector<GraphNode> nodes) {
   }
 }
 
-CommandEncoder& Device::get_command_encoder(Stream s) {
-  auto it = encoders_.find(s.index);
-  if (it == encoders_.end()) {
-    it = encoders_.try_emplace(s.index, *this).first;
-  }
-  return it->second;
-}
-
-CommandEncoder::CommandEncoder(Device& d) : stream_(d) {
+CommandEncoder::CommandEncoder(Device& d) : device_(d), stream_(d) {
   CHECK_CUDA_ERROR(cudaGraphCreate(&graph_, 0));
 }
 
@@ -216,12 +215,14 @@ void CommandEncoder::add_kernel_node(
     void* func,
     dim3 grid_dim,
     dim3 block_dim,
+    uint32_t smem_bytes,
     void** params) {
   cudaKernelNodeParams kernel_params = {0};
   kernel_params.func = func;
   kernel_params.gridDim = grid_dim;
   kernel_params.blockDim = block_dim;
   kernel_params.kernelParams = params;
+  kernel_params.sharedMemBytes = smem_bytes;
   cudaGraphNode_t node;
   CHECK_CUDA_ERROR(
       cudaGraphAddKernelNode(&node, graph_, NULL, 0, &kernel_params));
@@ -232,6 +233,7 @@ void CommandEncoder::add_kernel_node(
     CUfunction func,
     dim3 grid_dim,
     dim3 block_dim,
+    uint32_t smem_bytes,
     void** params) {
   CUDA_KERNEL_NODE_PARAMS kernel_params = {0};
   kernel_params.func = func;
@@ -242,6 +244,7 @@ void CommandEncoder::add_kernel_node(
   kernel_params.blockDimY = block_dim.y;
   kernel_params.blockDimZ = block_dim.z;
   kernel_params.kernelParams = params;
+  kernel_params.sharedMemBytes = smem_bytes;
   CUgraphNode node;
   CHECK_CUDA_ERROR(
       cuGraphAddKernelNode(&node, graph_, NULL, 0, &kernel_params));
@@ -264,22 +267,30 @@ void CommandEncoder::commit() {
     graph_key_ += std::to_string(graph_node_count_);
     graph_key_ += ".";
     graph_key_ += std::to_string(empty_node_count_);
-    auto [it, _] = graph_cache_.emplace(graph_key_, nullptr);
-    auto& graph_exec = it->second;
 
-    if (graph_exec != NULL) {
-      cudaGraphExecUpdateResultInfo update_result;
-      cudaGraphExecUpdate(graph_exec, graph_, &update_result);
-      if (update_result.result != cudaGraphExecUpdateSuccess) {
-        cudaGetLastError();
+    cudaGraphExec_t& graph_exec = graph_cache_[graph_key_];
+
+    if (graph_exec != nullptr) {
+      cudaGraphExecUpdateResult update_result;
+#if CUDART_VERSION >= 12000
+      cudaGraphExecUpdateResultInfo info;
+      cudaGraphExecUpdate(graph_exec, graph_, &info);
+      update_result = info.result;
+#else
+      cudaGraphNode_t error_node;
+      cudaGraphExecUpdate(graph_exec, graph_, &error_node, &update_result);
+#endif // CUDART_VERSION >= 12000
+      if (update_result != cudaGraphExecUpdateSuccess) {
+        cudaGetLastError(); // reset error
         CHECK_CUDA_ERROR(cudaGraphExecDestroy(graph_exec));
-        graph_exec = NULL;
+        graph_exec = nullptr;
       }
     }
-    if (graph_exec == NULL) {
+    if (graph_exec == nullptr) {
       CHECK_CUDA_ERROR(
           cudaGraphInstantiate(&graph_exec, graph_, NULL, NULL, 0));
     }
+    device_.make_current();
     CHECK_CUDA_ERROR(cudaGraphLaunch(graph_exec, stream_));
 
     // TODO smarter cache policy

mlx/backend/cuda/device.h

@@ -45,25 +45,34 @@ class CommandEncoder {
   void set_output_array(const array& arr);
 
   template <typename F, typename... Params>
-  void
-  add_kernel_node(F* func, dim3 grid_dim, dim3 block_dim, Params&&... params) {
+  void add_kernel_node(
+      F* func,
+      dim3 grid_dim,
+      dim3 block_dim,
+      uint32_t smem_bytes,
+      Params&&... params) {
     constexpr size_t num = sizeof...(Params);
     void* ptrs[num];
     size_t i = 0;
     ([&](auto&& p) { ptrs[i++] = static_cast<void*>(&p); }(
          std::forward<Params>(params)),
      ...);
-    add_kernel_node((void*)func, grid_dim, block_dim, ptrs);
+    add_kernel_node((void*)func, grid_dim, block_dim, smem_bytes, ptrs);
   }
 
   void add_kernel_node(
       CUfunction func,
       dim3 grid_dim,
       dim3 block_dim,
+      uint32_t smem_bytes,
       void** params);
 
-  void
-  add_kernel_node(void* func, dim3 grid_dim, dim3 block_dim, void** params);
+  void add_kernel_node(
+      void* func,
+      dim3 grid_dim,
+      dim3 block_dim,
+      uint32_t smem_bytes,
+      void** params);
 
   void add_temporary(const array& arr) {
     temporaries_.push_back(arr.data_shared_ptr());
@@ -93,6 +102,7 @@ class CommandEncoder {
   void insert_graph_dependencies(GraphNode node);
   void insert_graph_dependencies(std::vector<GraphNode> nodes);
 
+  Device& device_;
   CudaStream stream_;
   cudaGraph_t graph_;
   Worker worker_;

mlx/backend/cuda/device/atomic_ops.cuh

@@ -2,7 +2,7 @@
 
 #pragma once
 
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
+#include "mlx/backend/cuda/device/complex.cuh"
 #include "mlx/backend/cuda/device/fp16_math.cuh"
 
 #include <cuda/atomic>
@@ -48,7 +48,7 @@ inline __device__ void atomic_add(__half* out, __half val) {
   atomicAdd(out, val);
 }
 
-inline __device__ void atomic_add(cuComplex* out, cuComplex val) {
+inline __device__ void atomic_add(complex64_t* out, complex64_t val) {
 #if __CUDA_ARCH__ < 900
   atomic_add_general(out, val);
 #else
@@ -58,12 +58,7 @@ inline __device__ void atomic_add(cuComplex* out, cuComplex val) {
 
 inline __device__ void atomic_add(__nv_bfloat16* out, __nv_bfloat16 val) {
 #if __CUDA_ARCH__ < 800
-#if CCCL_VERSION >= 2008000
   atomic_add_general(out, val);
-#else
-  bool cccl_version_too_old_for_bfloat16_atomic_add = false;
-  assert(cccl_version_too_old_for_bfloat16_atomic_add);
-#endif
 #else
   atomicAdd(out, val);
 #endif

mlx/backend/cuda/device/binary_ops.cuh

@@ -1,10 +1,7 @@
 // Copyright © 2025 Apple Inc.
 
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
-#include "mlx/backend/cuda/device/fp16_math.cuh"
-#include "mlx/backend/cuda/device/utils.cuh"
+#include "mlx/backend/cuda/device/unary_ops.cuh"
 
-#include <cuComplex.h>
 #include <cuda/std/array>
 
 namespace mlx::core::cu {
@@ -47,7 +44,7 @@ struct Remainder {
       } else {
         return x % y;
       }
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
+    } else if constexpr (is_complex_v<T>) {
       return x % y;
     } else {
       T r = fmod(x, y);
@@ -69,14 +66,12 @@ struct Equal {
 struct NaNEqual {
   template <typename T>
   __device__ bool operator()(T x, T y) {
-    if constexpr (std::is_same_v<T, cuComplex>) {
+    if constexpr (is_complex_v<T>) {
       return x == y ||
-          (isnan(cuCrealf(x)) && isnan(cuCrealf(y)) && isnan(cuCimagf(x)) &&
-           isnan(cuCimagf(y))) ||
-          (cuCrealf(x) == cuCrealf(y) && isnan(cuCimagf(x)) &&
-           isnan(cuCimagf(y))) ||
-          (isnan(cuCrealf(x)) && isnan(cuCrealf(y)) &&
-           cuCimagf(x) == cuCimagf(y));
+          (isnan(x.real()) && isnan(y.real()) && isnan(x.imag()) &&
+           isnan(y.imag())) ||
+          (x.real() == y.real() && isnan(x.imag()) && isnan(y.imag())) ||
+          (isnan(x.real()) && isnan(y.real()) && x.imag() == y.imag());
     } else {
       return x == y || (isnan(x) && isnan(y));
     }
@@ -114,6 +109,27 @@ struct LessEqual {
 struct LogAddExp {
   template <typename T>
   __device__ T operator()(T x, T y) {
+    if constexpr (is_complex_v<T>) {
+      if (isnan(x.real()) || isnan(x.imag()) || isnan(y.real()) ||
+          isnan(y.imag())) {
+        return {
+            cuda::std::numeric_limits<float>::quiet_NaN(),
+            cuda::std::numeric_limits<float>::quiet_NaN()};
+      }
+      auto max = x.real() > y.real() ? x : y;
+      auto min = x.real() < y.real() ? x : y;
+      auto min_real = min.real();
+      auto max_real = max.real();
+      if (!isfinite(min_real) && (min_real == max_real)) {
+        if (min_real < 0) {
+          return min;
+        } else {
+          return Log{}(Exp{}(min) + Exp{}(max));
+        }
+      } else {
+        return Log1p{}(Exp{}(min - max)) + max;
+      }
+    } else {
       if (isnan(x) || isnan(y)) {
         return cuda::std::numeric_limits<T>::quiet_NaN();
       }
@@ -123,27 +139,8 @@ struct LogAddExp {
               maxval == cuda::std::numeric_limits<T>::infinity())
           ? maxval
           : T(float(maxval) + log1p(expf(minval - maxval)));
-  };
-
-  __device__ cuComplex operator()(cuComplex x, cuComplex y) {
-    if (isnan(cuCrealf(x)) || isnan(cuCimagf(x)) || isnan(cuCrealf(y)) ||
-        isnan(cuCimagf(y))) {
-      return {
-          cuda::std::numeric_limits<float>::quiet_NaN(),
-          cuda::std::numeric_limits<float>::quiet_NaN()};
     }
-    float inf = cuda::std::numeric_limits<float>::infinity();
-    auto maxval = x > y ? x : y;
-    auto minval = x < y ? x : y;
-    if (cuCrealf(minval) == -inf || cuCrealf(maxval) == inf)
-      return maxval;
-    float m = exp(cuCrealf(minval) - cuCrealf(maxval));
-    cuComplex dexp{
-        m * cos(cuCimagf(minval) - cuCimagf(maxval)),
-        m * sin(cuCimagf(minval) - cuCimagf(maxval)),
   };
-    return maxval + log1p(dexp);
-  }
 };
 
 struct Maximum {
@@ -151,8 +148,8 @@ struct Maximum {
   __device__ T operator()(T x, T y) {
     if constexpr (cuda::std::is_integral_v<T>) {
       return max(x, y);
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      if (isnan(cuCrealf(x)) || isnan(cuCimagf(x))) {
+    } else if constexpr (is_complex_v<T>) {
+      if (isnan(x.real()) || isnan(x.imag())) {
         return x;
       }
       return x > y ? x : y;
@@ -170,8 +167,8 @@ struct Minimum {
   __device__ T operator()(T x, T y) {
     if constexpr (cuda::std::is_integral_v<T>) {
       return min(x, y);
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      if (isnan(cuCrealf(x)) || isnan(cuCimagf(x))) {
+    } else if constexpr (is_complex_v<T>) {
+      if (isnan(x.real()) || isnan(x.imag())) {
         return x;
       }
       return x < y ? x : y;
@@ -194,8 +191,8 @@ struct Multiply {
 struct NotEqual {
   template <typename T>
   __device__ bool operator()(T x, T y) {
-    if constexpr (std::is_same_v<T, cuComplex>) {
-      return cuCrealf(x) != cuCrealf(y) || cuCimagf(x) != cuCimagf(y);
+    if constexpr (is_complex_v<T>) {
+      return x.real() != y.real() || x.imag() != y.imag();
     } else {
       return x != y;
     }
@@ -215,19 +212,8 @@ struct Power {
         base *= base;
       }
       return res;
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      if (base.y == 0 && base.x == 0) {
-        if (isnan(exp.x) || isnan(exp.y)) {
-          auto nan = cuda::std::numeric_limits<float>::quiet_NaN();
-          return make_cuFloatComplex(nan, nan);
-        }
-        return make_cuFloatComplex(0.0, 0.0);
-      }
-      auto x_theta = atan2f(base.y, base.x);
-      auto x_ln_r = 0.5 * logf(base.x * base.x + base.y * base.y);
-      auto mag = expf(exp.x * x_ln_r - exp.y * x_theta);
-      auto phase = exp.y * x_ln_r + exp.x * x_theta;
-      return make_cuFloatComplex(mag * cosf(phase), mag * sinf(phase));
+    } else if constexpr (is_complex_v<T>) {
+      return pow(base, exp);
     } else {
       return powf(base, exp);
     }

mlx/backend/cuda/device/cast_op.cuh

@@ -2,7 +2,10 @@
 
 #pragma once
 
-#include <cuComplex.h>
+#include "mlx/backend/cuda/device/complex.cuh"
+
+#include <cuda_bf16.h>
+#include <cuda_fp16.h>
 #include <thrust/iterator/transform_iterator.h>
 
 namespace mlx::core::cu {
@@ -17,34 +20,48 @@ struct CastOp {
   }
 };
 
-// Converting a complex number to real number discards the imaginary part.
-template <typename DstT>
-struct CastOp<
-    cuComplex,
-    DstT,
-    cuda::std::enable_if_t<!cuda::std::is_same_v<cuComplex, DstT>>> {
-  static constexpr bool is_castable = cuda::std::is_convertible_v<float, DstT>;
+// Castings between complex and boolean.
+template <typename T>
+struct CastOp<complex_t<T>, bool> {
+  static constexpr bool is_castable = true;
 
-  __device__ DstT operator()(cuComplex x) {
-    static_assert(!cuda::std::is_same_v<cuComplex, DstT>);
-    return static_cast<DstT>(cuCrealf(x));
+  __device__ bool operator()(complex_t<T> x) {
+    return x.real() != 0 && x.imag() != 0;
+  }
+};
+
+template <typename T>
+struct CastOp<bool, complex_t<T>> {
+  static constexpr bool is_castable = true;
+
+  __device__ complex_t<T> operator()(bool x) {
+    return x ? complex_t<T>{1, 1} : complex_t<T>{0, 0};
+  }
+};
+
+// Converting a complex number to real number discards the imaginary part.
+template <typename T, typename DstT>
+struct CastOp<complex_t<T>, DstT, cuda::std::enable_if_t<!is_complex_v<DstT>>> {
+  static constexpr bool is_castable = cuda::std::is_convertible_v<T, DstT>;
+
+  __device__ DstT operator()(complex_t<T> x) {
+    static_assert(!is_complex_v<DstT>);
+    return static_cast<DstT>(x.real());
   }
 };
 
 // Allow converting a real number to complex number.
-template <typename SrcT>
-struct CastOp<
-    SrcT,
-    cuComplex,
-    cuda::std::enable_if_t<!cuda::std::is_same_v<SrcT, cuComplex>>> {
-  static constexpr bool is_castable = cuda::std::is_convertible_v<SrcT, float>;
+template <typename SrcT, typename T>
+struct CastOp<SrcT, complex_t<T>, cuda::std::enable_if_t<!is_complex_v<SrcT>>> {
+  static constexpr bool is_castable = cuda::std::is_convertible_v<SrcT, T>;
 
-  __device__ cuComplex operator()(SrcT x) {
-    static_assert(!cuda::std::is_same_v<SrcT, cuComplex>);
-    return cuComplex{static_cast<float>(x), 0};
+  __device__ complex_t<T> operator()(SrcT x) {
+    static_assert(!is_complex_v<SrcT>);
+    return complex_t<T>{static_cast<T>(x), 0};
   }
 };
 
+// Do nothing when no casting is needed.
 template <typename SrcT, typename DstT>
 struct CastOp<
     SrcT,
@@ -57,9 +74,51 @@ struct CastOp<
   }
 };
 
+// In CUDA 11 the half types do not define conversions between some types,
+// provide fallbacks here.
+#if CUDART_VERSION < 12000
+template <typename SrcT, typename DstT>
+struct CastOp<
+    SrcT,
+    DstT,
+    cuda::std::enable_if_t<
+        !cuda::std::is_convertible_v<SrcT, DstT> && !is_complex_v<SrcT> &&
+        (cuda::std::is_same_v<DstT, __half> ||
+         cuda::std::is_same_v<DstT, __nv_bfloat16>)>> {
+  static constexpr bool is_castable = true;
+
+  __device__ DstT operator()(SrcT x) {
+    return DstT(static_cast<float>(x));
+  }
+};
+
+template <typename SrcT, typename DstT>
+struct CastOp<
+    SrcT,
+    DstT,
+    cuda::std::enable_if_t<
+        !cuda::std::is_convertible_v<SrcT, DstT> && !is_complex_v<SrcT> &&
+        !cuda::std::is_same_v<DstT, __half> &&
+        !cuda::std::is_same_v<DstT, __nv_bfloat16> &&
+        (cuda::std::is_same_v<SrcT, __half> ||
+         cuda::std::is_same_v<SrcT, __nv_bfloat16>)>> {
+  static constexpr bool is_castable = true;
+
+  __device__ DstT operator()(SrcT x) {
+    return DstT(static_cast<float>(x));
+  }
+};
+#endif // CUDART_VERSION < 12000
+
+// Helper to deduce the SrcT.
+template <typename DstT, typename SrcT>
+inline __host__ __device__ auto cast_to(SrcT x) {
+  return CastOp<SrcT, DstT>{}(x);
+}
+
 // Return an iterator that cast the value to DstT using CastOp.
 template <typename DstT, typename Iterator>
-__host__ __device__ auto make_cast_iterator(Iterator it) {
+inline __host__ __device__ auto make_cast_iterator(Iterator it) {
   using SrcT = typename cuda::std::iterator_traits<Iterator>::value_type;
   if constexpr (std::is_same_v<SrcT, DstT>) {
     return it;

mlx/backend/cuda/device/complex.cuh

@@ -0,0 +1,60 @@
+// Copyright © 2025 Apple Inc.
+
+#pragma once
+
+// Make multiplication and division faster.
+#define LIBCUDACXX_ENABLE_SIMPLIFIED_COMPLEX_OPERATIONS
+
+#include <cuda/std/complex>
+#include <cuda/std/type_traits>
+
+namespace mlx::core::cu {
+
+// TODO: Consider using a faster implementation as cuda::std::complex has to
+// conform to C++ standard.
+template <typename T>
+using complex_t = cuda::std::complex<T>;
+
+using complex64_t = complex_t<float>;
+using complex128_t = complex_t<double>;
+
+template <typename T>
+struct is_complex : cuda::std::false_type {};
+
+template <typename T>
+struct is_complex<cuda::std::complex<T>> : cuda::std::true_type {};
+
+template <typename T>
+inline constexpr bool is_complex_v = is_complex<T>::value;
+
+// cuda::std::complex is missing some operators.
+template <typename T>
+inline __host__ __device__ complex_t<T> operator%(
+    complex_t<T> a,
+    complex_t<T> b) {
+  T r = a.real() - floor(a.real() / b.real()) * b.real();
+  T i = a.imag() - floor(a.imag() / b.imag()) * b.imag();
+  return complex_t<T>{r, i};
+}
+
+template <typename T>
+inline __host__ __device__ bool operator>(complex_t<T> a, complex_t<T> b) {
+  return (a.real() > b.real()) || (a.real() == b.real() && a.imag() > b.imag());
+}
+
+template <typename T>
+inline __host__ __device__ bool operator<(complex_t<T> a, complex_t<T> b) {
+  return operator>(b, a);
+}
+
+template <typename T>
+inline __host__ __device__ bool operator<=(complex_t<T> a, complex_t<T> b) {
+  return !(a > b);
+}
+
+template <typename T>
+inline __host__ __device__ bool operator>=(complex_t<T> a, complex_t<T> b) {
+  return !(a < b);
+}
+
+} // namespace mlx::core::cu

mlx/backend/cuda/device/cucomplex_math.cuh

@@ -1,240 +0,0 @@
-// Copyright © 2025 Apple Inc.
-// Copyright © 2017-2024 The Simons Foundation, Inc.
-//
-// FINUFFT is licensed under the Apache License, Version 2.0 (the
-// "License"); you may not use this file except in compliance with the
-// License.  You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-//
-// Forked from
-// https://github.com/flatironinstitute/finufft/blob/main/include/cufinufft/contrib/helper_math.h
-
-#pragma once
-
-#include <cuComplex.h>
-
-// This header provides some helper functions for cuComplex types.
-// It mainly wraps existing CUDA implementations to provide operator overloads
-// e.g. cuAdd, cuSub, cuMul, cuDiv, cuCreal, cuCimag, cuCabs, cuCarg, cuConj are
-// all provided by CUDA
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator+(const cuDoubleComplex& a, const cuDoubleComplex& b) {
-  return cuCadd(a, b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator-(const cuDoubleComplex& a, const cuDoubleComplex& b) {
-  return cuCsub(a, b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator*(const cuDoubleComplex& a, const cuDoubleComplex& b) {
-  return cuCmul(a, b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator/(const cuDoubleComplex& a, const cuDoubleComplex& b) {
-  return cuCdiv(a, b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator%(const cuDoubleComplex& a, const cuDoubleComplex& b) {
-  double r = cuCreal(a) - (floorf(cuCreal(a) / cuCreal(b)) * cuCreal(b));
-  double i = cuCimag(a) - (floorf(cuCimag(a) / cuCimag(b)) * cuCimag(b));
-  return make_cuDoubleComplex(r, i);
-}
-
-__forceinline__ __host__ __device__ bool operator==(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  return cuCreal(a) == cuCreal(b) && cuCimag(a) == cuCimag(b);
-}
-
-__forceinline__ __host__ __device__ bool operator!=(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  return !(a == b);
-}
-
-__forceinline__ __host__ __device__ bool operator>(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  double mag_a = sqrt(cuCreal(a) * cuCreal(a) + cuCimag(a) * cuCimag(a));
-  double mag_b = sqrt(cuCreal(b) * cuCreal(b) + cuCimag(b) * cuCimag(b));
-  return mag_a > mag_b;
-}
-
-__forceinline__ __host__ __device__ bool operator>=(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  return a > b || a == b;
-}
-
-__forceinline__ __host__ __device__ bool operator<(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  return b > a;
-}
-
-__forceinline__ __host__ __device__ bool operator<=(
-    const cuDoubleComplex& a,
-    const cuDoubleComplex& b) {
-  return b > a || a == b;
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator+(const cuDoubleComplex& a, double b) {
-  return make_cuDoubleComplex(cuCreal(a) + b, cuCimag(a));
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator+(double a, const cuDoubleComplex& b) {
-  return make_cuDoubleComplex(a + cuCreal(b), cuCimag(b));
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator-(const cuDoubleComplex& a, double b) {
-  return make_cuDoubleComplex(cuCreal(a) - b, cuCimag(a));
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator-(double a, const cuDoubleComplex& b) {
-  return make_cuDoubleComplex(a - cuCreal(b), -cuCimag(b));
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator*(const cuDoubleComplex& a, double b) {
-  return make_cuDoubleComplex(cuCreal(a) * b, cuCimag(a) * b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator*(double a, const cuDoubleComplex& b) {
-  return make_cuDoubleComplex(a * cuCreal(b), a * cuCimag(b));
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator/(const cuDoubleComplex& a, double b) {
-  return make_cuDoubleComplex(cuCreal(a) / b, cuCimag(a) / b);
-}
-
-__forceinline__ __host__ __device__ cuDoubleComplex
-operator/(double a, const cuDoubleComplex& b) {
-  double denom = cuCreal(b) * cuCreal(b) + cuCimag(b) * cuCimag(b);
-  return make_cuDoubleComplex(
-      (a * cuCreal(b)) / denom, (-a * cuCimag(b)) / denom);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator+(const cuFloatComplex& a, const cuFloatComplex& b) {
-  return cuCaddf(a, b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator-(const cuFloatComplex& a, const cuFloatComplex& b) {
-  return cuCsubf(a, b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator*(const cuFloatComplex& a, const cuFloatComplex& b) {
-  return cuCmulf(a, b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator/(const cuFloatComplex& a, const cuFloatComplex& b) {
-  return cuCdivf(a, b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator%(const cuFloatComplex& a, const cuFloatComplex& b) {
-  float r = cuCrealf(a) - (floorf(cuCrealf(a) / cuCrealf(b)) * cuCrealf(b));
-  float i = cuCimagf(a) - (floorf(cuCimagf(a) / cuCimagf(b)) * cuCimagf(b));
-  return make_cuFloatComplex(r, i);
-}
-
-__forceinline__ __host__ __device__ bool operator==(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  return cuCrealf(a) == cuCrealf(b) && cuCimagf(a) == cuCimagf(b);
-}
-
-__forceinline__ __host__ __device__ bool operator!=(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  return !(a == b);
-}
-
-__forceinline__ __host__ __device__ bool operator>(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  float mag_a = sqrt(cuCrealf(a) * cuCrealf(a) + cuCimagf(a) * cuCimagf(a));
-  float mag_b = sqrt(cuCrealf(b) * cuCrealf(b) + cuCimagf(b) * cuCimagf(b));
-  return mag_a > mag_b;
-}
-
-__forceinline__ __host__ __device__ bool operator>=(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  return a > b || a == b;
-}
-
-__forceinline__ __host__ __device__ bool operator<(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  return b > a;
-}
-
-__forceinline__ __host__ __device__ bool operator<=(
-    const cuFloatComplex& a,
-    const cuFloatComplex& b) {
-  return b > a || a == b;
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator+(const cuFloatComplex& a, float b) {
-  return make_cuFloatComplex(cuCrealf(a) + b, cuCimagf(a));
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator+(float a, const cuFloatComplex& b) {
-  return make_cuFloatComplex(a + cuCrealf(b), cuCimagf(b));
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator-(const cuFloatComplex& a, float b) {
-  return make_cuFloatComplex(cuCrealf(a) - b, cuCimagf(a));
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator-(float a, const cuFloatComplex& b) {
-  return make_cuFloatComplex(a - cuCrealf(b), -cuCimagf(b));
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator*(const cuFloatComplex& a, float b) {
-  return make_cuFloatComplex(cuCrealf(a) * b, cuCimagf(a) * b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator*(float a, const cuFloatComplex& b) {
-  return make_cuFloatComplex(a * cuCrealf(b), a * cuCimagf(b));
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator/(const cuFloatComplex& a, float b) {
-  return make_cuFloatComplex(cuCrealf(a) / b, cuCimagf(a) / b);
-}
-
-__forceinline__ __host__ __device__ cuFloatComplex
-operator/(float a, const cuFloatComplex& b) {
-  float denom = cuCrealf(b) * cuCrealf(b) + cuCimagf(b) * cuCimagf(b);
-  return make_cuFloatComplex(
-      (a * cuCrealf(b)) / denom, (-a * cuCimagf(b)) / denom);
-}

mlx/backend/cuda/device/unary_ops.cuh

@@ -14,8 +14,6 @@ struct Abs {
   __device__ T operator()(T x) {
     if constexpr (cuda::std::is_unsigned_v<T>) {
       return x;
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {sqrt(cuCrealf(x) * cuCrealf(x) + cuCimagf(x) * cuCimagf(x)), 0};
     } else {
       return abs(x);
     }
@@ -27,8 +25,6 @@ struct ArcCos {
   __device__ T operator()(T x) {
     return acos(x);
   }
-
-  __device__ cuComplex operator()(cuComplex x);
 };
 
 struct ArcCosh {
@@ -43,8 +39,6 @@ struct ArcSin {
   __device__ T operator()(T x) {
     return asin(x);
   }
-
-  __device__ cuComplex operator()(cuComplex x);
 };
 
 struct ArcSinh {
@@ -59,8 +53,6 @@ struct ArcTan {
   __device__ T operator()(T x) {
     return atan(x);
   }
-
-  __device__ cuComplex operator()(cuComplex x);
 };
 
 struct ArcTanh {
@@ -82,6 +74,8 @@ struct Ceil {
   __device__ T operator()(T x) {
     if constexpr (cuda::std::is_integral_v<T>) {
       return x;
+    } else if constexpr (is_complex_v<T>) {
+      return T{ceil(x.real()), ceil(x.imag())};
     } else {
       return ceil(x);
     }
@@ -89,35 +83,24 @@ struct Ceil {
 };
 
 struct Conjugate {
-  __device__ cuComplex operator()(cuComplex x) {
-    return {cuCrealf(x), -cuCimagf(x)};
+  template <typename T>
+  __device__ complex_t<T> operator()(complex_t<T> x) {
+    return conj(x);
   }
 };
 
 struct Cos {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {
-          cos(cuCrealf(x)) * cosh(cuCimagf(x)),
-          -sin(cuCrealf(x)) * sinh(cuCimagf(x))};
-    } else {
     return cos(x);
   }
-  }
 };
 
 struct Cosh {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {
-          cosh(cuCrealf(x)) * cos(cuCimagf(x)),
-          sinh(cuCrealf(x)) * sin(cuCimagf(x))};
-    } else {
     return cosh(x);
   }
-  }
 };
 
 struct Erf {
@@ -149,13 +132,8 @@ struct ErfInv {
 struct Exp {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      auto m = exp(cuCrealf(x));
-      return {m * cos(cuCimagf(x)), m * sinh(cuCimagf(x))};
-    } else {
     return exp(x);
   }
-  }
 };
 
 struct Expm1 {
@@ -176,6 +154,8 @@ struct Floor {
   __device__ T operator()(T x) {
     if constexpr (cuda::std::is_integral_v<T>) {
       return x;
+    } else if constexpr (is_complex_v<T>) {
+      return T{floor(x.real()), floor(x.imag())};
     } else {
       return floor(x);
     }
@@ -183,30 +163,25 @@ struct Floor {
 };
 
 struct Imag {
-  __device__ float operator()(cuComplex x) {
-    return cuCimagf(x);
+  template <typename T>
+  __device__ auto operator()(complex_t<T> x) {
+    return x.imag();
   }
 };
 
 struct Log {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      auto r = log(cuCrealf(Abs{}(x)));
-      auto i = atan2f(cuCimagf(x), cuCrealf(x));
-      return {r, i};
-    } else {
     return log(x);
   }
-  }
 };
 
 struct Log2 {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
+    if constexpr (is_complex_v<T>) {
       auto y = Log{}(x);
-      return {cuCrealf(y) / CUDART_LN2_F, cuCimagf(y) / CUDART_LN2_F};
+      return {y.real() / CUDART_LN2_F, y.imag() / CUDART_LN2_F};
     } else {
       return log2(x);
     }
@@ -216,20 +191,31 @@ struct Log2 {
 struct Log10 {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      auto y = Log{}(x);
-      return {cuCrealf(y) / CUDART_LNT_F, cuCimagf(y) / CUDART_LNT_F};
-      return y;
-    } else {
     return log10(x);
   }
-  }
 };
 
 struct Log1p {
   template <typename T>
-  __device__ T operator()(T x) {
-    return log1p(x);
+  __device__ T operator()(T z) {
+    if constexpr (is_complex_v<T>) {
+      float x = z.real();
+      float y = z.imag();
+      float zabs = Abs{}(z).real();
+      float theta = atan2f(y, x + 1);
+      if (zabs < 0.5f) {
+        float r = x * (2 + x) + y * y;
+        if (r == 0) { // handle underflow
+          return {x, theta};
+        }
+        return {0.5f * log1pf(r), theta};
+      } else {
+        float z0 = hypotf(x + 1, y);
+        return {logf(z0), theta};
+      }
+    } else {
+      return log1p(z);
+    }
   }
 };
 
@@ -242,8 +228,8 @@ struct LogicalNot {
 struct Negative {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return 0 - x;
+    if constexpr (is_complex_v<T>) {
+      return T{0, 0} - x;
     } else {
       return -x;
     }
@@ -251,16 +237,17 @@ struct Negative {
 };
 
 struct Real {
-  __device__ float operator()(cuComplex x) {
-    return cuCrealf(x);
+  template <typename T>
+  __device__ auto operator()(complex_t<T> x) {
+    return x.real();
   }
 };
 
 struct Round {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {rint(cuCrealf(x)), rint(cuCimagf(x))};
+    if constexpr (is_complex_v<T>) {
+      return {rint(x.real()), rint(x.imag())};
     } else {
       return rint(x);
     }
@@ -280,8 +267,8 @@ struct Sign {
   __device__ T operator()(T x) {
     if constexpr (cuda::std::is_unsigned_v<T>) {
       return x != 0;
-    } else if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      if (cuCrealf(x) == 0 && cuCimagf(x) == 0) {
+    } else if constexpr (is_complex_v<T>) {
+      if (x.real() == 0 && x.imag() == 0) {
         return x;
       } else {
         return x / Abs()(x);
@@ -297,27 +284,15 @@ struct Sign {
 struct Sin {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {
-          sin(cuCrealf(x)) * cosh(cuCimagf(x)),
-          cos(cuCrealf(x)) * sinh(cuCimagf(x))};
-    } else {
     return sin(x);
   }
-  }
 };
 
 struct Sinh {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      return {
-          sinh(cuCrealf(x)) * cos(cuCimagf(x)),
-          cosh(cuCrealf(x)) * sin(cuCimagf(x))};
-    } else {
     return sinh(x);
   }
-  }
 };
 
 struct Square {
@@ -332,77 +307,31 @@ struct Sqrt {
   __device__ T operator()(T x) {
     return sqrt(x);
   }
-
-  __device__ cuComplex operator()(cuComplex x) {
-    auto xr = cuCrealf(x);
-    auto xi = cuCimagf(x);
-    if (xr == 0.0f && xi == 0.0f) {
-      return {0.0f, 0.0f};
-    }
-    auto r = cuCrealf(Abs{}(x));
-    auto a = sqrt((r + xr) / 2.0f);
-    auto b_abs = sqrt((r - xr) / 2.0f);
-    auto b = copysign(b_abs, xi);
-    return {a, b};
-  }
 };
 
 struct Rsqrt {
   template <typename T>
   __device__ T operator()(T x) {
+    if constexpr (is_complex_v<T>) {
+      return 1.0f / Sqrt{}(x);
+    } else {
       return rsqrt(x);
     }
-  __device__ cuComplex operator()(cuComplex x) {
-    return 1.0f / Sqrt{}(x);
   }
 };
 
 struct Tan {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      float tan_a = tan(cuCrealf(x));
-      float tanh_b = tanh(cuCimagf(x));
-      float t1 = tan_a * tanh_b;
-      float denom = 1. + t1 * t1;
-      return {(tan_a - tanh_b * t1) / denom, (tanh_b + tan_a * t1) / denom};
-    } else {
     return tan(x);
   }
-  }
 };
 
 struct Tanh {
   template <typename T>
   __device__ T operator()(T x) {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
-      float tanh_a = tanh(cuCrealf(x));
-      float tan_b = tan(cuCimagf(x));
-      float t1 = tanh_a * tan_b;
-      float denom = 1. + t1 * t1;
-      return {(tanh_a + tan_b * t1) / denom, (tan_b - tanh_a * t1) / denom};
-    } else {
     return tanh(x);
   }
-  }
-};
-
-__device__ cuComplex ArcCos::operator()(cuComplex x) {
-  auto i = cuComplex{0.0, 1.0};
-  auto y = Log{}(x + i * Sqrt{}(1.0 - x * x));
-  return {cuCimagf(y), -cuCrealf(y)};
-};
-
-__device__ cuComplex ArcSin::operator()(cuComplex x) {
-  auto i = cuComplex{0.0f, 1.0f};
-  auto y = Log{}(i * x + Sqrt{}(1.0f - x * x));
-  return {cuCimagf(y), -cuCrealf(y)};
-};
-
-__device__ cuComplex ArcTan::operator()(cuComplex x) {
-  auto i = cuComplex{0.0f, 1.0f};
-  auto ix = i * x;
-  return (1.0f / cuComplex{0.0f, 2.0f}) * Log{}((1.0f + ix) / (1.0f - ix));
 };
 
 } // namespace mlx::core::cu

mlx/backend/cuda/device/utils.cuh

@@ -8,9 +8,9 @@
 
 #pragma once
 
+#include "mlx/backend/cuda/device/complex.cuh"
 #include "mlx/backend/cuda/device/config.h"
 
-#include <cuComplex.h>
 #include <cuda_bf16.h>
 #include <cuda_fp16.h>
 #include <cuda/std/array>
@@ -28,6 +28,27 @@ namespace mlx::core::cu {
 using Shape = cuda::std::array<int32_t, MAX_NDIM>;
 using Strides = cuda::std::array<int64_t, MAX_NDIM>;
 
+// Vectorized load/store.
+template <typename T, int N>
+struct alignas(sizeof(T) * N) AlignedVector {
+  T val[N];
+};
+
+template <int N, typename T>
+inline __device__ AlignedVector<T, N> load_vector(
+    const T* ptr,
+    uint32_t offset) {
+  auto* from = reinterpret_cast<const AlignedVector<T, N>*>(ptr);
+  return from[offset];
+}
+
+template <int N, typename T>
+inline __device__ void
+store_vector(T* ptr, uint32_t offset, const AlignedVector<T, N>& vec) {
+  auto* to = reinterpret_cast<AlignedVector<T, N>*>(ptr);
+  to[offset] = vec;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 // Type limits utils
 ///////////////////////////////////////////////////////////////////////////////
@@ -78,20 +99,20 @@ struct Limits<
     return cuda::std::numeric_limits<T>::infinity();
   }
   static constexpr __host__ __device__ T min() {
-#if defined(__CUDA_ARCH__) || CUDART_VERSION >= 12000
-    return -cuda::std::numeric_limits<T>::infinity();
-#else
+#if CUDART_VERSION < 12000 && __CUDA_ARCH__ < 800
     return -cuda::std::numeric_limits<float>::infinity();
+#else
+    return -cuda::std::numeric_limits<T>::infinity();
 #endif
   }
   static constexpr __host__ __device__ T finite_max() {
     return cuda::std::numeric_limits<T>::max();
   }
   static constexpr __host__ __device__ T finite_min() {
-#if defined(__CUDA_ARCH__) || CUDART_VERSION >= 12000
-    return cuda::std::numeric_limits<T>::lowest();
-#else
+#if CUDART_VERSION < 12000 && __CUDA_ARCH__ < 800
     return cuda::std::numeric_limits<float>::lowest();
+#else
+    return cuda::std::numeric_limits<T>::lowest();
 #endif
   }
 };
@@ -106,13 +127,13 @@ struct Limits<bool> {
   }
 };
 
-template <>
-struct Limits<cuComplex> {
-  static constexpr __host__ __device__ cuComplex max() {
-    return {Limits<float>::max(), Limits<float>::max()};
+template <typename T>
+struct Limits<complex_t<T>> {
+  static constexpr __host__ __device__ complex_t<T> max() {
+    return {Limits<T>::max(), Limits<T>::max()};
   }
-  static constexpr __host__ __device__ cuComplex min() {
-    return {Limits<float>::min(), Limits<float>::min()};
+  static constexpr __host__ __device__ complex_t<T> min() {
+    return {Limits<T>::min(), Limits<T>::min()};
   }
 };
 
@@ -338,21 +359,4 @@ struct LoopedElemToLoc<1, false, OffsetT> {
   }
 };
 
-inline __device__ cuComplex log1p(cuComplex in) {
-  float x = cuCrealf(in);
-  float y = cuCimagf(in);
-  float zabs = sqrt(x * x + y * y);
-  float theta = atan2f(y, x + 1);
-  if (zabs < 0.5f) {
-    float r = x * (2 + x) + y * y;
-    if (r == 0) { // handle underflow
-      return {x, theta};
-    }
-    return {0.5f * log1pf(r), theta};
-  } else {
-    auto z0 = sqrt((x + 1) * (x + 1) + y * y);
-    return {log(z0), theta};
-  }
-}
-
 } // namespace mlx::core::cu

mlx/backend/cuda/event.cu

@@ -90,8 +90,6 @@ bool CudaEvent::completed() const {
 // SharedEvent implementations
 ///////////////////////////////////////////////////////////////////////////////
 
-namespace {
-
 __host__ __device__ void event_wait(SharedEvent::Atomic* ac, uint64_t value) {
   uint64_t current;
   while ((current = ac->load()) < value) {
@@ -112,8 +110,6 @@ __global__ void event_signal_kernel(SharedEvent::Atomic* ac, uint64_t value) {
   event_signal(ac, value);
 }
 
-} // namespace
-
 SharedEvent::SharedEvent() {
   // Allocate cuda::atomic on managed memory.
   Atomic* ac;

mlx/backend/cuda/indexing.cpp

@@ -129,7 +129,7 @@ void Gather::eval_gpu(const std::vector<array>& inputs, array& out) {
 
   auto kernel = mod.get_kernel(kernel_name);
   auto [num_blocks, block_dims] = get_launch_args(kernel, out, large);
-  encoder.add_kernel_node(kernel, num_blocks, block_dims, args.args());
+  encoder.add_kernel_node(kernel, num_blocks, block_dims, 0, args.args());
 }
 
 void Scatter::eval_gpu(const std::vector<array>& inputs, array& out) {
@@ -230,7 +230,7 @@ void Scatter::eval_gpu(const std::vector<array>& inputs, array& out) {
   encoder.set_output_array(out);
   auto kernel = mod.get_kernel(kernel_name);
   auto [num_blocks, block_dims] = get_launch_args(kernel, upd, large);
-  encoder.add_kernel_node(kernel, num_blocks, block_dims, args.args());
+  encoder.add_kernel_node(kernel, num_blocks, block_dims, 0, args.args());
 }
 
 void GatherAxis::eval_gpu(const std::vector<array>& inputs, array& out) {
@@ -318,7 +318,7 @@ void GatherAxis::eval_gpu(const std::vector<array>& inputs, array& out) {
   encoder.set_output_array(out);
   auto kernel = mod.get_kernel(kernel_name);
   auto [num_blocks, block_dims] = get_launch_args(kernel, idx, large);
-  encoder.add_kernel_node(kernel, num_blocks, block_dims, args.args());
+  encoder.add_kernel_node(kernel, num_blocks, block_dims, 0, args.args());
 }
 
 void ScatterAxis::eval_gpu(const std::vector<array>& inputs, array& out) {
@@ -422,7 +422,7 @@ void ScatterAxis::eval_gpu(const std::vector<array>& inputs, array& out) {
   encoder.set_output_array(out);
   auto kernel = mod.get_kernel(kernel_name);
   auto [num_blocks, block_dims] = get_launch_args(kernel, idx, large);
-  encoder.add_kernel_node(kernel, num_blocks, block_dims, args.args());
+  encoder.add_kernel_node(kernel, num_blocks, block_dims, 0, args.args());
 }
 
 } // namespace mlx::core

mlx/backend/cuda/jit_module.cpp

@@ -2,6 +2,7 @@
 
 #include "mlx/backend/cuda/jit_module.h"
 #include "mlx/backend/cuda/device.h"
+#include "mlx/version.h"
 
 #include "cuda_jit_sources.h"
 
@@ -12,6 +13,7 @@
 
 #include <fmt/format.h>
 #include <nvrtc.h>
+#include <unistd.h>
 
 namespace mlx::core::cu {
 
@@ -49,14 +51,41 @@ const std::string& cuda_home() {
   return home;
 }
 
+// Return the location of CCCL headers shipped with the distribution.
+const std::string& cccl_dir() {
+  static std::string dir = []() {
+    std::filesystem::path path;
+#if defined(MLX_CCCL_DIR)
+    // First search the install dir if defined.
+    path = MLX_CCCL_DIR;
+    if (std::filesystem::exists(path)) {
+      return path.string();
+    }
+#endif
+    // Then search dynamically from the dir of libmlx.so file.
+    path = current_binary_dir().parent_path() / "include" / "cccl";
+    if (std::filesystem::exists(path)) {
+      return path.string();
+    }
+    // Finally check the environment variable.
+    path = std::getenv("MLX_CCCL_DIR");
+    if (!path.empty() && std::filesystem::exists(path)) {
+      return path.string();
+    }
+    return std::string();
+  }();
+  return dir;
+}
+
 // Get the cache directory for storing compiled results.
 const std::filesystem::path& ptx_cache_dir() {
   static std::filesystem::path cache = []() -> std::filesystem::path {
     std::filesystem::path cache;
-    if (auto c = std::getenv("MLX_PTX_CACHE"); c) {
+    if (auto c = std::getenv("MLX_PTX_CACHE_DIR"); c) {
       cache = c;
     } else {
-      cache = std::filesystem::temp_directory_path() / "mlx" / "ptx";
+      cache =
+          std::filesystem::temp_directory_path() / "mlx" / version() / "ptx";
     }
     if (!std::filesystem::exists(cache)) {
       std::error_code error;
@@ -108,7 +137,8 @@ void write_cached_ptx(
     const std::filesystem::path& cache_dir,
     const std::string& module_name,
     const std::vector<char>& ptx,
-    const std::vector<std::pair<std::string, std::string>>& ptx_kernels) {
+    const std::vector<std::pair<std::string, std::string>>& ptx_kernels,
+    const std::string& source_code) {
   if (cache_dir.empty()) {
     return;
   }
@@ -121,6 +151,9 @@ void write_cached_ptx(
   for (const auto& [name, mangled] : ptx_kernels) {
     txt_file << name << "\t" << mangled << std::endl;
   }
+
+  std::ofstream source_file(cache_dir / (module_name + ".cu"));
+  source_file << source_code;
 }
 
 // Return if |device|'s version is not newer than |major|.|minor| version.
@@ -160,7 +193,7 @@ constexpr const char* g_include_names[] = {
     INCLUDE_PREFIX "binary_ops.cuh",
     INCLUDE_PREFIX "cast_op.cuh",
     INCLUDE_PREFIX "config.h",
-    INCLUDE_PREFIX "cucomplex_math.cuh",
+    INCLUDE_PREFIX "complex.cuh",
     INCLUDE_PREFIX "fp16_math.cuh",
     INCLUDE_PREFIX "indexing.cuh",
     INCLUDE_PREFIX "scatter_ops.cuh",
@@ -176,7 +209,7 @@ constexpr const char* g_headers[] = {
     jit_source_binary_ops,
     jit_source_cast_op,
     jit_source_config,
-    jit_source_cucomplex_math,
+    jit_source_complex,
     jit_source_fp16_math,
     jit_source_indexing,
     jit_source_scatter_ops,
@@ -213,16 +246,24 @@ JitModule::JitModule(
     }
 
     // Compile program.
+    std::vector<const char*> args;
     bool use_sass = compiler_supports_device_sass(device);
     std::string compute = fmt::format(
         "--gpu-architecture={}_{}{}",
         use_sass ? "sm" : "compute",
         device.compute_capability_major(),
         device.compute_capability_minor());
-    std::string include = fmt::format("--include-path={}/include", cuda_home());
-    const char* args[] = {compute.c_str(), include.c_str()};
+    args.push_back(compute.c_str());
+    std::string cccl_include = cccl_dir();
+    if (!cccl_include.empty()) {
+      cccl_include = fmt::format("--include-path={}", cccl_include);
+      args.push_back(cccl_include.c_str());
+    }
+    std::string cuda_include =
+        fmt::format("--include-path={}/include", cuda_home());
+    args.push_back(cuda_include.c_str());
     nvrtcResult compile_result =
-        nvrtcCompileProgram(prog, std::size(args), args);
+        nvrtcCompileProgram(prog, args.size(), args.data());
     if (compile_result != NVRTC_SUCCESS) {
       size_t log_size;
       CHECK_NVRTC_ERROR(nvrtcGetProgramLogSize(prog, &log_size));
@@ -252,7 +293,8 @@ JitModule::JitModule(
     } else {
       CHECK_NVRTC_ERROR(nvrtcGetPTX(prog, ptx.data()));
     }
-    write_cached_ptx(ptx_cache_dir(), module_name, ptx, ptx_kernels);
+    write_cached_ptx(
+        ptx_cache_dir(), module_name, ptx, ptx_kernels, source_code);
   }
 
   // Load module.

mlx/backend/cuda/kernel_utils.cuh

@@ -11,7 +11,6 @@
 #include "mlx/array.h"
 #include "mlx/backend/cuda/device/utils.cuh"
 
-#include <cuComplex.h>
 #include <cuda.h>
 #include <cuda_bf16.h>
 #include <cuda_fp16.h>
@@ -79,7 +78,7 @@ struct CTypeToCudaType<bfloat16_t> {
 
 template <>
 struct CTypeToCudaType<complex64_t> {
-  using type = cuComplex;
+  using type = cu::complex64_t;
 };
 
 template <typename T>
@@ -91,10 +90,14 @@ inline constexpr bool is_floating_v =
     cuda::std::is_same_v<T, float> || cuda::std::is_same_v<T, double> ||
     cuda::std::is_same_v<T, float16_t> || cuda::std::is_same_v<T, bfloat16_t>;
 
+// Type traits for detecting complex numbers.
+template <typename T>
+inline constexpr bool is_complex_v = cuda::std::is_same_v<T, complex64_t> ||
+    cuda::std::is_same_v<T, complex128_t>;
+
 // Type traits for detecting complex or real floating point numbers.
 template <typename T>
-inline constexpr bool is_inexact_v =
-    is_floating_v<T> || cuda::std::is_same_v<T, complex64_t>;
+inline constexpr bool is_inexact_v = is_floating_v<T> || is_complex_v<T>;
 
 // Utility to copy data from vector to array in host.
 template <int NDIM = MAX_NDIM, typename T = int32_t>

mlx/backend/cuda/layer_norm.cu

@@ -237,8 +237,7 @@ void LayerNorm::eval_gpu(
       }
       return x;
     } else {
-      auto x_copy = array(x.shape(), x.dtype(), nullptr, {});
-      copy_gpu(x, x_copy, CopyType::General, s);
+      array x_copy = contiguous_copy_gpu(x, s);
       out.copy_shared_buffer(x_copy);
       return x_copy;
     }
@@ -267,6 +266,7 @@ void LayerNorm::eval_gpu(
           kernel,
           n_rows,
           block_dim(),
+          0,
           x.data<DataType>(),
           w.data<DataType>(),
           b.data<DataType>(),
@@ -295,9 +295,7 @@ void LayerNormVJP::eval_gpu(
       return x;
     }
     copied = true;
-    array x_copy(x.shape(), x.dtype(), nullptr, {});
-    copy_gpu(x, x_copy, CopyType::General, s);
-    return x_copy;
+    return contiguous_copy_gpu(x, s);
   };
   bool donate_x = inputs[0].is_donatable();
   bool donate_g = inputs[3].is_donatable();
@@ -381,6 +379,7 @@ void LayerNormVJP::eval_gpu(
                 kernel,
                 n_rows,
                 block_dim(),
+                0,
                 x.data<DataType>(),
                 w.data<DataType>(),
                 g.data<DataType>(),

mlx/backend/cuda/logsumexp.cu

@@ -108,8 +108,7 @@ void LogSumExp::eval_gpu(const std::vector<array>& inputs, array& out) {
     if (x.flags().contiguous && x.strides()[x.ndim() - 1] == 1) {
       return x;
     } else {
-      auto x_copy = array(x.shape(), x.dtype(), nullptr, {});
-      copy_gpu(x, x_copy, CopyType::General, s);
+      array x_copy = contiguous_copy_gpu(x, s);
       encoder.add_temporary(x_copy);
       return x_copy;
     }
@@ -152,6 +151,7 @@ void LogSumExp::eval_gpu(const std::vector<array>& inputs, array& out) {
           kernel,
           n_rows,
           block_dim(),
+          0,
           in.data<DataType>(),
           out.data<DataType>(),
           axis_size);

mlx/backend/cuda/matmul.cpp

@@ -27,6 +27,35 @@ void check_cublas_error(const char* name, cublasStatus_t err) {
   }
 }
 
+struct CublasPreference {
+  CublasPreference(Device& device) {
+    // The recommended cublas workspace size is 4 MiB for pre-Hopper and 32 MiB
+    // for Hopper+:
+    // https://docs.nvidia.com/cuda/cublas/#cublassetworkspace
+    uint64_t MiB = 1024 * 1024;
+    uint64_t workspace_size =
+        device.compute_capability_major() >= 9 ? 32 * MiB : 4 * MiB;
+
+    CHECK_CUBLAS_ERROR(cublasLtMatmulPreferenceCreate(&pref_));
+    CHECK_CUBLAS_ERROR(cublasLtMatmulPreferenceSetAttribute(
+        pref_,
+        CUBLASLT_MATMUL_PREF_MAX_WORKSPACE_BYTES,
+        &workspace_size,
+        sizeof(uint64_t)));
+  }
+
+  ~CublasPreference() {
+    CHECK_CUBLAS_ERROR(cublasLtMatmulPreferenceDestroy(pref_));
+  }
+
+  cublasLtMatmulPreference_t pref_{nullptr};
+};
+
+cublasLtMatmulPreference_t cublas_preference(Device& device) {
+  static CublasPreference pref(device);
+  return pref.pref_;
+}
+
 class MatMul {
  public:
   MatMul(
@@ -43,7 +72,7 @@ class MatMul {
       int32_t batch_count,
       int64_t a_batch_stride,
       int64_t b_batch_stride)
-      : handle_(device.lt_handle()) {
+      : handle_(device.lt_handle()), pref_(cublas_preference(device)) {
     heuristic_.state = CUBLAS_STATUS_NOT_INITIALIZED;
 
     auto scale_type = dtype_to_cuda_type(dtype);
@@ -77,20 +106,6 @@ class MatMul {
         type, b_rows, b_cols, b_transposed, ldb, batch_count, b_batch_stride);
     out_desc_ = create_matrix_layout(
         type, a_rows, b_cols, false, b_cols, batch_count, a_rows * b_cols);
-
-    // The recommended cublas workspace size is 4 MiB for pre-Hopper and 32 MiB
-    // for Hopper+:
-    // https://docs.nvidia.com/cuda/cublas/#cublassetworkspace
-    uint64_t MiB = 1024 * 1024;
-    uint64_t workspace_size =
-        device.compute_capability_major() >= 9 ? 32 * MiB : 4 * MiB;
-
-    CHECK_CUBLAS_ERROR(cublasLtMatmulPreferenceCreate(&pref_));
-    CHECK_CUBLAS_ERROR(cublasLtMatmulPreferenceSetAttribute(
-        pref_,
-        CUBLASLT_MATMUL_PREF_MAX_WORKSPACE_BYTES,
-        &workspace_size,
-        sizeof(uint64_t)));
   }
 
   MatMul(
@@ -104,7 +119,6 @@ class MatMul {
       uint64_t b_rows,
       uint64_t b_cols,
       int64_t ldb,
-      bool c_transposed,
       int64_t ldc,
       int32_t batch_count,
       int64_t a_batch_stride,
@@ -126,15 +140,15 @@ class MatMul {
             b_batch_stride) {
     auto type = dtype_to_cuda_type(dtype);
     c_desc_ = create_matrix_layout(
-        type, a_rows, b_cols, c_transposed, ldc, batch_count, c_batch_stride);
+        type, a_rows, b_cols, false, ldc, batch_count, c_batch_stride);
   }
 
   ~MatMul() {
-    cublasLtMatrixLayoutDestroy(a_desc_);
-    cublasLtMatrixLayoutDestroy(b_desc_);
-    cublasLtMatrixLayoutDestroy(c_desc_);
-    cublasLtMatrixLayoutDestroy(out_desc_);
-    cublasLtMatmulDescDestroy(matmul_desc_);
+    CHECK_CUBLAS_ERROR(cublasLtMatrixLayoutDestroy(a_desc_));
+    CHECK_CUBLAS_ERROR(cublasLtMatrixLayoutDestroy(b_desc_));
+    CHECK_CUBLAS_ERROR(cublasLtMatrixLayoutDestroy(c_desc_));
+    CHECK_CUBLAS_ERROR(cublasLtMatrixLayoutDestroy(out_desc_));
+    CHECK_CUBLAS_ERROR(cublasLtMatmulDescDestroy(matmul_desc_));
   }
 
   void run(
@@ -259,9 +273,9 @@ class MatMul {
     return desc;
   }
 
+  cublasLtMatmulPreference_t pref_{nullptr};
   cublasLtHandle_t handle_{nullptr};
   cublasLtMatmulDesc_t matmul_desc_{nullptr};
-  cublasLtMatmulPreference_t pref_{nullptr};
   cublasLtMatrixLayout_t a_desc_{nullptr};
   cublasLtMatrixLayout_t b_desc_{nullptr};
   cublasLtMatrixLayout_t c_desc_{nullptr};
@@ -282,8 +296,7 @@ check_transpose(cu::CommandEncoder& enc, const Stream& s, const array& arr) {
   } else if (stx == 1 && sty == arr.shape(-2)) {
     return std::make_tuple(true, sty, arr);
   } else {
-    array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
-    copy_gpu(arr, arr_copy, CopyType::General, s);
+    array arr_copy = contiguous_copy_gpu(arr, s);
     enc.add_temporary(arr_copy);
     return std::make_tuple(false, arr.shape(-1), arr_copy);
   }
@@ -389,9 +402,7 @@ void AddMM::eval_gpu(const std::vector<array>& inputs, array& out) {
   assert(inputs.size() == 3);
   auto& a_pre = inputs[0];
   auto& b_pre = inputs[1];
-  auto& c_pre = inputs[2];
-
-  out.set_data(allocator::malloc(out.nbytes()));
+  auto c = inputs[2];
 
   /////////////////////////////////////////////////////////////////////////////
   // Init checks and prep
@@ -404,7 +415,24 @@ void AddMM::eval_gpu(const std::vector<array>& inputs, array& out) {
   // the arrays
   auto [a_transposed, lda, a] = check_transpose(encoder, s, a_pre);
   auto [b_transposed, ldb, b] = check_transpose(encoder, s, b_pre);
-  auto [c_transposed, ldc, c] = check_transpose(encoder, s, c_pre);
+
+  int64_t ldc;
+  {
+    auto stx = c.strides()[c.ndim() - 2];
+    auto sty = c.strides()[c.ndim() - 1];
+    if (sty == 1 && stx == c.shape(-1)) {
+      ldc = stx;
+      out.set_data(allocator::malloc(out.nbytes()));
+    } else if (sty == 1 && stx == 0) {
+      ldc = 0;
+      out.set_data(allocator::malloc(out.nbytes()));
+    } else {
+      // Copy C into out and set C to out
+      ldc = c.shape(-1);
+      copy_gpu(c, out, CopyType::General, s);
+      c = out;
+    }
+  }
 
   /////////////////////////////////////////////////////////////////////////////
   // Check and collapse batch dimensions
@@ -442,7 +470,6 @@ void AddMM::eval_gpu(const std::vector<array>& inputs, array& out) {
       K,
       N,
       ldb,
-      c_transposed,
       ldc,
       batch_shape.back(),
       a_batch_strides.back(),

mlx/backend/cuda/matmul/mma.cuh

@@ -0,0 +1,108 @@
+// Copyright © 2025 Apple Inc.
+
+#pragma once
+
+#include "mlx/backend/cuda/matmul/tiles.cuh"
+
+namespace mlx::core::cu {
+
+template <typename U, typename T>
+__device__ inline void
+mma_t(Tile16x16<U>& C, Tile16x16<T>& A, Tile16x16<T>& B) {}
+
+/**
+ * Multiply the 16x16 bfloat16 tiles and accumulate the result in one 16x16
+ * float tile.
+ *
+ * We actually perform C += A @ B.T
+ */
+__device__ inline void mma_t(
+    Tile16x16<float>& C,
+    Tile16x16<__nv_bfloat16>& A,
+    Tile16x16<__nv_bfloat16>& B) {
+  asm volatile(
+      "mma.sync.aligned.m16n8k16.row.col.f32.bf16.bf16.f32 "
+      "{%0, %1, %2, %3}, "
+      "{%4, %5, %6, %7}, "
+      "{%8, %9}, "
+      "{%10, %11, %12, %13};"
+
+      // D matrix
+      : "+f"(C.values[0].x),
+        "+f"(C.values[0].y),
+        "+f"(C.values[1].x),
+        "+f"(C.values[1].y)
+
+      // A matrix
+      : "r"(*(uint32_t*)(&A.values[0])),
+        "r"(*(uint32_t*)(&A.values[1])),
+        "r"(*(uint32_t*)(&A.values[2])),
+        "r"(*(uint32_t*)(&A.values[3])),
+
+        // B matrix
+        "r"(*(uint32_t*)(&B.values[0])),
+        "r"(*(uint32_t*)(&B.values[2])),
+
+        // C matrix
+        "f"(C.values[0].x),
+        "f"(C.values[0].y),
+        "f"(C.values[1].x),
+        "f"(C.values[1].y));
+  asm volatile(
+      "mma.sync.aligned.m16n8k16.row.col.f32.bf16.bf16.f32 "
+      "{%0, %1, %2, %3}, "
+      "{%4, %5, %6, %7}, "
+      "{%8, %9}, "
+      "{%10, %11, %12, %13};"
+
+      // D matrix
+      : "+f"(C.values[2].x),
+        "+f"(C.values[2].y),
+        "+f"(C.values[3].x),
+        "+f"(C.values[3].y)
+
+      // A matrix
+      : "r"(*(uint32_t*)(&A.values[0])),
+        "r"(*(uint32_t*)(&A.values[1])),
+        "r"(*(uint32_t*)(&A.values[2])),
+        "r"(*(uint32_t*)(&A.values[3])),
+
+        // B matrix
+        "r"(*(uint32_t*)(&B.values[1])),
+        "r"(*(uint32_t*)(&B.values[3])),
+
+        // C matrix
+        "f"(C.values[2].x),
+        "f"(C.values[2].y),
+        "f"(C.values[3].x),
+        "f"(C.values[3].y));
+}
+
+/**
+ * Multiply larger register tiles by delegating to mma_t.
+ */
+template <typename U, typename T, int M, int N, int K>
+__device__ inline void mma_t(
+    RegisterTile<U, M, N>& C,
+    RegisterTile<T, M, K>& A,
+    RegisterTile<T, N, K>& B) {
+  constexpr int TILES_M = RegisterTile<T, M, K>::TILES_Y;
+  constexpr int TILES_K = RegisterTile<T, M, K>::TILES_X;
+  constexpr int TILES_N = RegisterTile<T, N, K>::TILES_Y;
+
+  MLX_UNROLL
+  for (int k = 0; k < TILES_K; k++) {
+    MLX_UNROLL
+    for (int m = 0; m < TILES_M; m++) {
+      MLX_UNROLL
+      for (int n = 0; n < TILES_N; n++) {
+        mma_t(
+            C.data[m * TILES_N + n],
+            A.data[m * TILES_K + k],
+            B.data[n * TILES_K + k]);
+      }
+    }
+  }
+}
+
+} // namespace mlx::core::cu

mlx/backend/cuda/matmul/tiles.cuh

@@ -0,0 +1,419 @@
+// Copyright © 2025 Apple Inc.
+
+#pragma once
+
+#define MLX_UNROLL _Pragma("unroll")
+
+namespace mlx::core::cu {
+
+// Map types to their vector of 2 type float -> float2, double -> double2 etc
+template <typename T>
+struct Vector2;
+template <>
+struct Vector2<double> {
+  using type = double2;
+};
+template <>
+struct Vector2<float> {
+  using type = float2;
+};
+template <>
+struct Vector2<__half> {
+  using type = __half2;
+};
+template <>
+struct Vector2<__nv_bfloat16> {
+  using type = __nv_bfloat162;
+};
+template <typename T>
+using Vector2_t = typename Vector2<T>::type;
+
+/**
+ * The basic building block for Ampere mmas. A 16x16 tile distributed across
+ * the warp.
+ *
+ * Each thread holds 8 values. They are distributed according to
+ * https://docs.nvidia.com/cuda/parallel-thread-execution/#warp-level-matrix-fragment-mma-16816-float
+ *
+ * For use instructions see the individual methods eg load().
+ */
+template <typename T>
+struct Tile16x16 {
+  using T2 = Vector2_t<T>;
+
+  T2 values[4];
+
+  __device__ inline void fill(T v) {
+    T2 v2 = {v, v};
+    for (int i = 0; i < 4; i++) {
+      values[i] = v2;
+    }
+  }
+
+  /**
+   * Load a 16x16 tile from shared memory.
+   *
+   * The instruction is a bit weird in the sense that the address provided by
+   * each thread and the elements loaded are not the same.
+   *
+   * We load 4 8x8 tiles. The tile rows are stored contiguously in memory. As a
+   * result the warp provides 4*8 = 32 addresses one per row.
+   *
+   * Threads 0-7 provide the addresses for the first tile, 8-15 for the second
+   * and so on. For instance to load a non swizzled tile we would do
+   *
+   *    base_addr + (laneid % 16) * BK + (laneid / 2) * 8
+   *
+   * See
+   * https://docs.nvidia.com/cuda/parallel-thread-execution/#warp-level-matrix-instructions-ldmatrix
+   */
+  __device__ inline void load(uint32_t row_address) {
+    if constexpr (
+        std::is_same_v<T2, __nv_bfloat162> || std::is_same_v<T2, __half2>) {
+      asm volatile(
+          "ldmatrix.sync.aligned.m8n8.x4.shared::cta.b16 {%0, %1, %2, %3}, [%4];\n"
+          : "=r"(*(uint32_t*)&(values[0])),
+            "=r"(*(uint32_t*)&(values[1])),
+            "=r"(*(uint32_t*)&(values[2])),
+            "=r"(*(uint32_t*)&(values[3]))
+          : "r"(row_address));
+    }
+  }
+
+  /**
+   * Store the tile to the address pointed to by `x`.
+   *
+   * The provided pointer is a generic pointer but this is meant to be used to
+   * store to global memory. For storing to shared memory we should use
+   * `stmatrix`.
+   *
+   * This also showcases the format of the tile quite nicely. Each register is
+   * holding to adjacent values. The indices are
+   *
+   *    row + 0, col + 0
+   *    row + 8, col + 0
+   *    row + 0, col + 8
+   *    row + 8, col + 8
+   *
+   * Given that we are dealing with Vector2_t<U> the column offsets are 4
+   * instead of 8.
+   */
+  template <typename U>
+  __device__ inline void store_global(U* x, int N) {
+    using U2 = Vector2_t<U>;
+    U2* x2 = reinterpret_cast<U2*>(x);
+    const int laneid = threadIdx.x % 32;
+    const int row = laneid / 4;
+    const int col = laneid % 4;
+    if constexpr (std::is_same_v<U2, T2>) {
+      x2[(row + 0) * (N / 2) + col + 0] = values[0];
+      x2[(row + 0) * (N / 2) + col + 4] = values[2];
+      x2[(row + 8) * (N / 2) + col + 0] = values[1];
+      x2[(row + 8) * (N / 2) + col + 4] = values[3];
+    } else if constexpr (
+        std::is_same_v<T2, float2> && std::is_same_v<U, __nv_bfloat16>) {
+      x2[(row + 0) * (N / 2) + col + 0] =
+          __floats2bfloat162_rn(values[0].x, values[0].y);
+      x2[(row + 0) * (N / 2) + col + 4] =
+          __floats2bfloat162_rn(values[2].x, values[2].y);
+      x2[(row + 8) * (N / 2) + col + 0] =
+          __floats2bfloat162_rn(values[1].x, values[1].y);
+      x2[(row + 8) * (N / 2) + col + 4] =
+          __floats2bfloat162_rn(values[3].x, values[3].y);
+    }
+  }
+
+  template <typename U>
+  __device__ inline void store_global_safe(U* x, int N, int max_rows) {
+    const int laneid = threadIdx.x % 32;
+    const int row = laneid / 4;
+    const int col = laneid % 4;
+    if (row < max_rows) {
+      x[(row + 0) * N + 2 * col + 0] = static_cast<U>(values[0].x);
+      x[(row + 0) * N + 2 * col + 1] = static_cast<U>(values[0].y);
+      x[(row + 0) * N + 2 * col + 8] = static_cast<U>(values[2].x);
+      x[(row + 0) * N + 2 * col + 9] = static_cast<U>(values[2].y);
+    }
+    if (row + 8 < max_rows) {
+      x[(row + 8) * N + 2 * col + 0] = static_cast<U>(values[1].x);
+      x[(row + 8) * N + 2 * col + 1] = static_cast<U>(values[1].y);
+      x[(row + 8) * N + 2 * col + 8] = static_cast<U>(values[3].x);
+      x[(row + 8) * N + 2 * col + 9] = static_cast<U>(values[3].y);
+    }
+  }
+};
+
+/**
+ * A simple container of multiple Tile16x16.
+ *
+ * Provides utility functions for loading and manipulating collections of basic
+ * tiles.
+ */
+template <typename T, int ROWS_, int COLS_>
+struct RegisterTile {
+  static constexpr int ROWS = ROWS_;
+  static constexpr int COLS = COLS_;
+  static constexpr int TILES_X = COLS / 16;
+  static constexpr int TILES_Y = ROWS / 16;
+
+  Tile16x16<T> data[TILES_X * TILES_Y];
+
+  __device__ inline void fill(T v) {
+    MLX_UNROLL
+    for (int i = 0; i < TILES_Y; i++) {
+      MLX_UNROLL
+      for (int j = 0; j < TILES_X; j++) {
+        data[i * TILES_X + j].fill(v);
+      }
+    }
+  }
+
+  template <typename Tile>
+  __device__ inline void
+  load(Tile& tile, uint32_t base_address, int row, int col) {
+    MLX_UNROLL
+    for (int i = 0; i < TILES_Y; i++) {
+      MLX_UNROLL
+      for (int j = 0; j < TILES_X; j++) {
+        data[i * TILES_X + j].load(
+            tile.loc(base_address, row + i * 16, col + j * 16));
+      }
+    }
+  }
+
+  template <typename U>
+  __device__ inline void store_global(U* x, int N, int row, int col) {
+    MLX_UNROLL
+    for (int i = 0; i < TILES_Y; i++) {
+      MLX_UNROLL
+      for (int j = 0; j < TILES_X; j++) {
+        data[i * TILES_X + j].store_global(
+            x + (row + i * 16) * N + col + j * 16, N);
+      }
+    }
+  }
+
+  template <typename U>
+  __device__ inline void
+  store_global_safe(U* x, int N, int row, int col, int max_rows) {
+    MLX_UNROLL
+    for (int i = 0; i < TILES_Y; i++) {
+      MLX_UNROLL
+      for (int j = 0; j < TILES_X; j++) {
+        data[i * TILES_X + j].store_global_safe(
+            x + (row + i * 16) * N + col + j * 16, N, max_rows - row - i * 16);
+      }
+    }
+  }
+};
+
+template <typename T, int ROWS_, int COLS_>
+struct SharedTile {
+  static constexpr int ROWS = ROWS_;
+  static constexpr int COLS = COLS_;
+  static constexpr int TILES_X = COLS / 16;
+  static constexpr int TILES_Y = ROWS / 16;
+  static constexpr int NUMEL = ROWS * COLS;
+
+  // Swizzle taken from ThunderKittens.
+  //
+  // See inludes/types/shared/st.cuh
+  //
+  // I do feel that it is too math heavy and can be improved. Also the math is
+  // done every time although the addresses don't change from load to load. I
+  // guess we are expecting the compiler to figure that out.
+  static constexpr int swizzle_bytes =
+      (sizeof(T) == 2 ? (TILES_X % 4 == 0 ? 128 : (TILES_X % 2 == 0 ? 64 : 32))
+                      : (sizeof(T) == 4 ? (TILES_X % 2 == 0 ? 128 : 64) : 0));
+
+  T data[ROWS * COLS];
+
+  // Return a pointer to the element at (row, col) using the swizzle.
+  __device__ static inline T* ptr(T* ptr, int row, int col) {
+    if constexpr (swizzle_bytes > 0) {
+      static constexpr int swizzle_repeat = swizzle_bytes * 8;
+      static constexpr int subtile_cols = swizzle_bytes / sizeof(T);
+      const int outer_idx = col / subtile_cols;
+      const uint64_t addr =
+          (uint64_t)(&ptr
+                         [outer_idx * ROWS * subtile_cols + row * subtile_cols +
+                          col % subtile_cols]);
+      const int swizzle = ((addr % swizzle_repeat) >> 7) << 4;
+      return (T*)(addr ^ swizzle);
+    } else {
+      return ptr + row * COLS + col;
+    }
+  }
+
+  // Return the location of the element at (row, col) using the swizzle.
+  __device__ static inline uint32_t loc(uint32_t ptr, int row, int col) {
+    if constexpr (swizzle_bytes > 0) {
+      static constexpr int swizzle_repeat = swizzle_bytes * 8;
+      static constexpr int subtile_cols = swizzle_bytes / sizeof(T);
+      const int outer_idx = col / subtile_cols;
+      const uint32_t addr = ptr +
+          sizeof(T) *
+              (outer_idx * ROWS * subtile_cols + row * subtile_cols +
+               col % subtile_cols);
+      const int swizzle = ((addr % swizzle_repeat) >> 7) << 4;
+      return (addr ^ swizzle);
+    } else {
+      return ptr + sizeof(T) * (row * COLS + col);
+    }
+  }
+
+  // Convenience functions to edit elements going through the swizzle.
+  __device__ inline T& operator()(int row, int col) {
+    return *ptr(data, row, col);
+  }
+  __device__ inline void store(float4& v, int row, int col) {
+    *(reinterpret_cast<float4*>(ptr(data, row, col))) = v;
+  }
+  __device__ inline void store(float2& v, int row, int col) {
+    *(reinterpret_cast<float2*>(ptr(data, row, col))) = v;
+  }
+  __device__ inline void store(float& v, int row, int col) {
+    *(reinterpret_cast<float*>(ptr(data, row, col))) = v;
+  }
+  template <int N>
+  __device__ inline void store(T (&v)[N], int row, int col) {
+    if constexpr (sizeof(T) * N == 4) {
+      store(*(reinterpret_cast<float*>(&v[0])), row, col);
+    } else if constexpr (sizeof(T) * N == 8) {
+      store(*(reinterpret_cast<float2*>(&v[0])), row, col);
+    } else if constexpr (sizeof(T) * N == 16) {
+      store(*(reinterpret_cast<float4*>(&v[0])), row, col);
+    } else {
+      MLX_UNROLL
+      for (int i = 0; i < N; i++) {
+        *ptr(data, row, col + i) = v[i];
+      }
+    }
+  }
+};
+
+/**
+ * Load the tile from global memory by loading 16 bytes at a time and storing
+ * them immediately.
+ */
+template <int NUM_WARPS, typename T, typename Tile>
+__device__ inline void load(Tile& tile, const T* x, int N) {
+  constexpr int NUM_THREADS = NUM_WARPS * 32;
+  constexpr int ELEMENTS_PER_LOAD = sizeof(float4) / sizeof(T);
+  constexpr int NUM_LOADS = Tile::NUMEL / ELEMENTS_PER_LOAD;
+  constexpr int NUM_LOADS_PER_THREAD = NUM_LOADS / NUM_THREADS;
+  constexpr int NUM_LOADS_PER_ROW = Tile::COLS / ELEMENTS_PER_LOAD;
+  constexpr int STEP_ROWS = NUM_THREADS / NUM_LOADS_PER_ROW;
+
+  const int row = threadIdx.x / NUM_LOADS_PER_ROW;
+  const int col = threadIdx.x % NUM_LOADS_PER_ROW;
+
+  x += row * N + col * ELEMENTS_PER_LOAD;
+
+  MLX_UNROLL
+  for (int i = 0; i < NUM_LOADS_PER_THREAD; i++) {
+    float4 tmp;
+    tmp = *(reinterpret_cast<const float4*>(&x[i * STEP_ROWS * N]));
+    tile.store(tmp, row + i * STEP_ROWS, col * ELEMENTS_PER_LOAD);
+  }
+}
+
+/**
+ * Copy 16 bytes from the globale memory address pointed to by x to the smem
+ * address pointed to by row_address.
+ *
+ * A simple wrapper over the PTX.
+ */
+template <typename T>
+__device__ inline void cp_async_16(uint32_t row_address, const T* x) {
+  asm volatile(
+      "cp.async.ca.shared::cta.global [%0], [%1], 16;\n" ::"r"(row_address),
+      "l"(reinterpret_cast<const int4*>(x)));
+}
+
+/**
+ * Submit all the previous async copies to be executed.
+ */
+__device__ inline void cp_async_commit() {
+  asm volatile("cp.async.commit_group;\n" ::);
+}
+
+/**
+ * Wait for all the async copies to finish.
+ */
+__device__ inline void cp_async_wait_all() {
+  asm volatile("cp.async.wait_all;\n" ::);
+}
+
+/**
+ * The asynchronous equivalent of load.
+ *
+ * Loads the tile from global memory by submitting a bunch of async copy
+ * instructions. The copy won't start until commit is called and we don't have
+ * a guarantee it will finish until wait is called.
+ *
+ * It should be used as follows
+ *
+ *    load(...)
+ *    load(...)
+ *    cp_async_commit()
+ *    do_other_stuff()
+ *    cp_async_wait_all()
+ *    do_stuff_with_shmem()
+ */
+template <int NUM_WARPS, typename T, typename Tile>
+__device__ inline void
+load_async(Tile& tile, uint32_t base_address, const T* x, int N) {
+  constexpr int NUM_THREADS = NUM_WARPS * 32;
+  constexpr int ELEMENTS_PER_LOAD = sizeof(float4) / sizeof(T);
+  constexpr int NUM_LOADS = Tile::NUMEL / ELEMENTS_PER_LOAD;
+  constexpr int NUM_LOADS_PER_THREAD = NUM_LOADS / NUM_THREADS;
+  constexpr int NUM_LOADS_PER_ROW = Tile::COLS / ELEMENTS_PER_LOAD;
+  constexpr int STEP_ROWS = NUM_THREADS / NUM_LOADS_PER_ROW;
+
+  const int row = threadIdx.x / NUM_LOADS_PER_ROW;
+  const int col = threadIdx.x % NUM_LOADS_PER_ROW;
+
+  x += row * N + col * ELEMENTS_PER_LOAD;
+
+  MLX_UNROLL
+  for (int i = 0; i < NUM_LOADS_PER_THREAD; i++) {
+    cp_async_16(
+        tile.loc(base_address, row + i * STEP_ROWS, col * ELEMENTS_PER_LOAD),
+        x + i * STEP_ROWS * N);
+  }
+}
+
+template <int NUM_WARPS, typename T, typename Tile>
+__device__ inline void load_async_safe(
+    Tile& tile,
+    uint32_t base_address,
+    const T* x,
+    int N,
+    int max_rows) {
+  constexpr int NUM_THREADS = NUM_WARPS * 32;
+  constexpr int ELEMENTS_PER_LOAD = sizeof(float4) / sizeof(T);
+  constexpr int NUM_LOADS = Tile::NUMEL / ELEMENTS_PER_LOAD;
+  constexpr int NUM_LOADS_PER_THREAD = NUM_LOADS / NUM_THREADS;
+  constexpr int NUM_LOADS_PER_ROW = Tile::COLS / ELEMENTS_PER_LOAD;
+  constexpr int STEP_ROWS = NUM_THREADS / NUM_LOADS_PER_ROW;
+
+  const int row = threadIdx.x / NUM_LOADS_PER_ROW;
+  const int col = threadIdx.x % NUM_LOADS_PER_ROW;
+
+  x += row * N + col * ELEMENTS_PER_LOAD;
+
+  MLX_UNROLL
+  for (int i = 0; i < NUM_LOADS_PER_THREAD; i++) {
+    if (row + i * STEP_ROWS < max_rows) {
+      cp_async_16(
+          tile.loc(base_address, row + i * STEP_ROWS, col * ELEMENTS_PER_LOAD),
+          x + i * STEP_ROWS * N);
+    } else {
+      float4 tmp = {0, 0, 0, 0};
+      tile.store(tmp, row + i * STEP_ROWS, col * ELEMENTS_PER_LOAD);
+    }
+  }
+}
+
+} // namespace mlx::core::cu

mlx/backend/cuda/primitives.cu

@@ -81,8 +81,7 @@ NO_GPU(Hadamard)
 NO_GPU(Load)
 NO_GPU_MULTI(LUF)
 NO_GPU_MULTI(QRF)
-NO_GPU(QuantizedMatmul)
-NO_GPU(Scan)
+NO_GPU(SegmentedMM)
 NO_GPU_MULTI(SVD)
 NO_GPU(Inverse)
 NO_GPU(Cholesky)
@@ -91,7 +90,6 @@ NO_GPU_MULTI(Eigh)
 
 namespace fast {
 NO_GPU(ScaledDotProductAttention)
-NO_GPU_MULTI(AffineQuantize)
 NO_GPU_MULTI(CustomKernel)
 } // namespace fast
 

mlx/backend/cuda/quantized/affine_quantize.cu

@@ -0,0 +1,331 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/backend/cuda/device.h"
+#include "mlx/backend/cuda/kernel_utils.cuh"
+#include "mlx/backend/cuda/quantized/quantized_utils.cuh"
+#include "mlx/dtype_utils.h"
+
+#include <cooperative_groups.h>
+#include <cooperative_groups/reduce.h>
+
+namespace mlx::core {
+namespace cu {
+
+namespace cg = cooperative_groups;
+
+template <typename T, int group_size, int bits>
+__global__ void
+affine_quantize(const T* w, uint8_t* out, T* scales, T* biases, size_t size) {
+  auto block_size = cg::this_thread_block().dim_threads();
+  auto block_idx = cg::this_thread_block().group_index();
+  auto idx_in_block = cg::this_thread_block().thread_index();
+
+  auto tidx = block_idx.x * block_size.x + idx_in_block.x;
+  auto tidy = block_idx.y * block_size.y + idx_in_block.y;
+
+  auto grid_dim_x =
+      cg::this_grid().dim_blocks().x * cg::this_grid().block_index().x;
+  constexpr float eps = 1e-7;
+  constexpr int simd_size = WARP_SIZE;
+  constexpr float n_bins = (1 << bits) - 1;
+  constexpr int pack_factor = get_pack_factor<bits, 8>();
+  constexpr int bytes_per_pack = get_bytes_per_pack<bits>();
+  constexpr int values_per_reduce = group_size / simd_size;
+  constexpr int writes_per_reduce = pack_factor / values_per_reduce;
+  constexpr int writes_per_pack =
+      writes_per_reduce > 1 ? 1 : values_per_reduce / pack_factor;
+  constexpr int power_of_2_bits = (bits & (bits - 1)) == 0;
+
+  size_t offset = tidx + grid_dim_x * size_t(tidy);
+  size_t in_index = offset * values_per_reduce;
+  if (in_index >= size) {
+    return;
+  }
+  size_t out_index = power_of_2_bits
+      ? offset * writes_per_pack
+      : offset * bytes_per_pack / writes_per_reduce;
+
+  float w_thread[values_per_reduce];
+  float w_min = Limits<float>::max();
+  float w_max = 0;
+
+#pragma clang loop unroll(full)
+  for (int i = 0; i < values_per_reduce; i++) {
+    float val = w[in_index + i];
+    w_thread[i] = val;
+    w_min = min(w_min, val);
+    w_max = max(w_max, val);
+  }
+
+  cg::greater<float> max_op;
+  cg::less<float> min_op;
+  auto warp = cg::tiled_partition<WARP_SIZE>(cg::this_thread_block());
+
+  w_min = cg::reduce(warp, w_min, min_op);
+  w_max = cg::reduce(warp, w_max, max_op);
+
+  float scale = max((w_max - w_min) / n_bins, eps);
+  bool side = abs(w_min) > abs(w_max);
+  scale = side ? scale : -scale;
+  float edge = side ? w_min : w_max;
+  float q0 = round(edge / scale);
+  bool at_zero = q0 == 0.0f;
+  scale = at_zero ? scale : edge / q0;
+  float bias = at_zero ? 0 : edge;
+
+  // Write out the scales and biases
+  size_t gindex = in_index / group_size;
+  if (in_index % group_size == 0) {
+    scales[gindex] = static_cast<T>(scale);
+    biases[gindex] = static_cast<T>(bias);
+  }
+
+  using OutType = std::conditional_t<bits == 5, uint64_t, uint32_t>;
+  OutType output = 0;
+
+#pragma clang loop unroll(full)
+  for (int i = 0; i < values_per_reduce; i++) {
+    uint8_t val = min(round((w_thread[i] - bias) / scale), n_bins);
+    if (bits == 8) {
+      output = val;
+    } else {
+      output |= val << (bits * (i % pack_factor));
+    }
+
+    if (pack_factor < values_per_reduce && i % pack_factor == pack_factor - 1) {
+      out[out_index + i / pack_factor] = output;
+      output = 0;
+    } else {
+#pragma clang loop unroll(full)
+      for (int j = 1; j < writes_per_reduce; j++) {
+        uint8_t sval = warp.shfl_down(val, j);
+        output |= static_cast<OutType>(sval)
+            << (bits * (j * values_per_reduce + i));
+      }
+    }
+  }
+  if constexpr (bits == 3 || bits == 6) {
+    if (in_index % pack_factor == 0 && out_index % bytes_per_pack == 0) {
+      out[out_index] = output & 0xff;
+      out[out_index + 1] = (output & 0xff00) >> 8;
+      out[out_index + 2] = (output & 0xff0000) >> 16;
+    }
+  } else if constexpr (bits == 5) {
+    if (in_index % pack_factor == 0 && out_index % bytes_per_pack == 0) {
+      out[out_index] = output & 0xff;
+      out[out_index + 1] = (output & 0xff00) >> 8;
+      out[out_index + 2] = (output & 0xff0000) >> 16;
+      out[out_index + 3] = (output & 0xff000000) >> 24;
+      out[out_index + 4] = (output & 0xff00000000) >> 32;
+    }
+  } else {
+    if constexpr (writes_per_reduce > 0) {
+      if (out_index % writes_per_reduce == 0) {
+        out[out_index / writes_per_reduce] = output;
+      }
+    }
+  }
+}
+
+template <typename T, int group_size, int bits>
+__global__ void affine_dequantize(
+    const uint8_t* w,
+    const T* scales,
+    const T* biases,
+    T* out,
+    size_t size) {
+  auto block_size = cg::this_thread_block().dim_threads();
+  auto block_idx = cg::this_thread_block().group_index();
+  auto idx_in_block = cg::this_thread_block().thread_index();
+
+  auto tidx = block_idx.x * block_size.x + idx_in_block.x;
+  auto tidy = block_idx.y * block_size.y + idx_in_block.y;
+
+  auto grid_dim_x =
+      cg::this_grid().dim_blocks().x * cg::this_grid().block_index().x;
+
+  constexpr int pack_factor = get_pack_factor<bits, 8>();
+  constexpr int bytes_per_pack = get_bytes_per_pack<bits>();
+
+  size_t offset = tidx + grid_dim_x * size_t(tidy);
+  size_t oindex = offset * pack_factor;
+
+  if (oindex >= size) {
+    return;
+  }
+
+  size_t gindex = oindex / group_size;
+  T scale = scales[gindex];
+  T bias = biases[gindex];
+  out += oindex;
+
+  if constexpr (bits == 3) {
+    w += offset * bytes_per_pack;
+    out[0] = static_cast<T>(w[0] & 0x7) * scale + bias;
+    out[1] = static_cast<T>((w[0] & 0x38) >> 3) * scale + bias;
+    out[2] = (static_cast<T>((w[0] & 0xc0) >> 6) +
+              static_cast<T>((w[1] & 0x1) << 2)) *
+            scale +
+        bias;
+    out[3] = static_cast<T>((w[1] & 0xe) >> 1) * scale + bias;
+    out[4] = static_cast<T>((w[1] & 0x70) >> 4) * scale + bias;
+    out[5] = (static_cast<T>((w[1] & 0x80) >> 7) +
+              static_cast<T>((w[2] & 0x3) << 1)) *
+            scale +
+        bias;
+    out[6] = static_cast<T>((w[2] & 0x1c) >> 2) * scale + bias;
+    out[7] = static_cast<T>((w[2] & 0xe0) >> 5) * scale + bias;
+  } else if constexpr (bits == 5) {
+    w += offset * bytes_per_pack;
+    out[0] = static_cast<T>(w[0] & 0x1f) * scale + bias;
+    out[1] = (static_cast<T>((w[0] & 0xe0) >> 5) +
+              static_cast<T>((w[1] & 0x3) << 3)) *
+            scale +
+        bias;
+    out[2] = static_cast<T>((w[1] & 0x7c) >> 2) * scale + bias;
+    out[3] = (static_cast<T>((w[1] & 0x80) >> 7) +
+              static_cast<T>((w[2] & 0xf) << 1)) *
+            scale +
+        bias;
+    out[4] = (static_cast<T>((w[2] & 0xf0) >> 4) +
+              static_cast<T>((w[3] & 0x1) << 4)) *
+            scale +
+        bias;
+    out[5] = static_cast<T>((w[3] & 0x3e) >> 1) * scale + bias;
+    out[6] = (static_cast<T>((w[3] & 0xc0) >> 6) +
+              static_cast<T>((w[4] & 0x7) << 2)) *
+            scale +
+        bias;
+    out[7] = static_cast<T>((w[4] & 0xf8) >> 3) * scale + bias;
+  } else if constexpr (bits == 6) {
+    w += offset * bytes_per_pack;
+    out[0] = static_cast<T>(w[0] & 0x3f) * scale + bias;
+    out[1] = (static_cast<T>((w[0] >> 6) & 0x03) +
+              static_cast<T>((w[1] & 0x0f) << 2)) *
+            scale +
+        bias;
+    out[2] = (static_cast<T>((w[1] >> 4) & 0x0f) +
+              static_cast<T>((w[2] & 0x03) << 4)) *
+            scale +
+        bias;
+    out[3] = static_cast<T>((w[2] >> 2) & 0x3f) * scale + bias;
+  } else {
+    uint val = w[offset];
+#pragma clang loop unroll(full)
+    for (int i = 0; i < pack_factor; i++) {
+      uint8_t d;
+      if (bits == 2) {
+        d = (val >> (bits * i)) & 0x03;
+      } else if (bits == 4) {
+        d = (val >> (bits * i)) & 0x0f;
+      } else if (bits == 8) {
+        d = val;
+      }
+      out[i] = scale * static_cast<T>(d) + bias;
+    }
+  }
+}
+
+} // namespace cu
+
+void affine_quantize(
+    const array& w,
+    array& wq,
+    array& scales,
+    array& biases,
+    int group_size_,
+    int bits_,
+    cu::CommandEncoder& enc,
+    const Stream& s) {
+  // Calculate the number of elements per thread
+  int per_thread = group_size_ / WARP_SIZE;
+  size_t size = w.size() / per_thread;
+
+  // Calculate the thread grid that we need to launch
+  bool large = size > UINT_MAX;
+  auto grid_shape = w.shape();
+  grid_shape.back() /= per_thread;
+
+  enc.set_input_array(w);
+  enc.set_output_array(wq);
+  enc.set_output_array(scales);
+  enc.set_output_array(biases);
+  dispatch_float_types(w.dtype(), "affine_quantize", [&](auto type_tag) {
+    dispatch_groups(group_size_, [&](auto group_size) {
+      dispatch_bits(bits_, [&](auto bits) {
+        using T = cuda_type_t<MLX_GET_TYPE(type_tag)>;
+        auto kernel = cu::affine_quantize<T, group_size.value, bits.value>;
+        auto [num_blocks, block_dims] =
+            get_launch_args(kernel, size, grid_shape, w.strides(), large);
+        enc.add_kernel_node(
+            kernel,
+            num_blocks,
+            block_dims,
+            0,
+            w.data<T>(),
+            wq.data<uint8_t>(),
+            scales.data<T>(),
+            biases.data<T>(),
+            w.size());
+      });
+    });
+  });
+}
+
+void affine_dequantize(
+    const array& wq,
+    const array& scales,
+    const array& biases,
+    array& w,
+    int group_size_,
+    int bits_,
+    cu::CommandEncoder& enc,
+    const Stream& s) {
+  // Calculate how many numbers we pack together. For 2, 4, 8 bits we pack in
+  // one uint8, for 3, 6 in 3 uint8 and for 5 in 5 uint8.
+  constexpr int uint8_per_uint32 = 4;
+  int packs_per_int;
+  switch (bits_) {
+    case 3:
+    case 5:
+      packs_per_int = 8;
+      break;
+    case 6:
+      packs_per_int = 4;
+      break;
+    default:
+      packs_per_int = 8 / bits_;
+  }
+
+  size_t size = w.size() / packs_per_int;
+  bool large = size > UINT_MAX;
+  auto grid_shape = w.shape();
+  grid_shape.back() *= uint8_per_uint32;
+
+  enc.set_input_array(wq);
+  enc.set_input_array(scales);
+  enc.set_input_array(biases);
+  enc.set_output_array(w);
+  dispatch_float_types(w.dtype(), "affine_quantize", [&](auto type_tag) {
+    dispatch_groups(group_size_, [&](auto group_size) {
+      dispatch_bits(bits_, [&](auto bits) {
+        using T = cuda_type_t<MLX_GET_TYPE(type_tag)>;
+        auto kernel = cu::affine_dequantize<T, group_size.value, bits.value>;
+        auto [num_blocks, block_dims] =
+            get_launch_args(kernel, size, grid_shape, w.strides(), large);
+        enc.add_kernel_node(
+            kernel,
+            num_blocks,
+            block_dims,
+            0,
+            wq.data<uint8_t>(),
+            scales.data<T>(),
+            biases.data<T>(),
+            w.data<T>(),
+            w.size());
+      });
+    });
+  });
+}
+
+} // namespace mlx::core

mlx/backend/cuda/quantized/qmm.cu

@@ -0,0 +1,228 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/backend/cuda/device.h"
+#include "mlx/backend/cuda/kernel_utils.cuh"
+#include "mlx/backend/cuda/matmul/mma.cuh"
+#include "mlx/backend/cuda/matmul/tiles.cuh"
+#include "mlx/backend/cuda/quantized/quantized_utils.cuh"
+#include "mlx/dtype_utils.h"
+
+namespace mlx::core {
+
+namespace cu {
+
+template <int NUM_WARPS, int group_size, int bits, typename T, typename Tile>
+__device__ inline void load_quantized(
+    Tile& tile,
+    const uint8_t* x,
+    const T* scales,
+    const T* biases,
+    int N) {
+  constexpr int NUM_THREADS = NUM_WARPS * 32;
+  constexpr int ELEMENTS_PER_LOAD = sizeof(uint32_t) * get_pack_factor<bits>();
+  constexpr int NUM_LOADS = Tile::NUMEL / ELEMENTS_PER_LOAD;
+  constexpr int NUM_LOADS_PER_THREAD = NUM_LOADS / NUM_THREADS;
+  constexpr int NUM_LOADS_PER_ROW = Tile::COLS / ELEMENTS_PER_LOAD;
+  constexpr int STEP_ROWS = NUM_THREADS / NUM_LOADS_PER_ROW;
+  constexpr int MASK = (1 << bits) - 1;
+
+  const int row = threadIdx.x / NUM_LOADS_PER_ROW;
+  const int col = threadIdx.x % NUM_LOADS_PER_ROW;
+
+  const int Nx = N / get_pack_factor<bits>();
+  const int Ng = N / group_size;
+
+  x += row * Nx + col * (ELEMENTS_PER_LOAD / get_pack_factor<bits>());
+  scales += row * Ng + col * ELEMENTS_PER_LOAD / group_size;
+  biases += row * Ng + col * ELEMENTS_PER_LOAD / group_size;
+
+  MLX_UNROLL
+  for (int i = 0; i < NUM_LOADS_PER_THREAD; i++) {
+    T vs[ELEMENTS_PER_LOAD];
+    uint32_t w = *reinterpret_cast<const uint32_t*>(x + i * STEP_ROWS * Nx);
+    T s = scales[i * STEP_ROWS * Ng];
+    T b = biases[i * STEP_ROWS * Ng];
+    MLX_UNROLL
+    for (int j = 0; j < ELEMENTS_PER_LOAD; j++) {
+      vs[j] = static_cast<T>((w >> (j * bits)) & MASK) * s + b;
+    }
+    tile.store(vs, row + i * STEP_ROWS, col * ELEMENTS_PER_LOAD);
+  }
+}
+
+template <
+    typename T,
+    int BM,
+    int BN,
+    int BK,
+    int group_size,
+    int bits,
+    bool aligned_M>
+__global__ void qmm_t(
+    const T* x,
+    const uint8_t* w,
+    const T* scales,
+    const T* biases,
+    T* y,
+    int M,
+    int N,
+    int K) {
+  constexpr int WARPS_M = 2;
+  constexpr int WARPS_N = 4;
+  constexpr int NUM_WARPS = WARPS_M * WARPS_N;
+  constexpr int WARP_STEP_M = BM / WARPS_M;
+  constexpr int WARP_STEP_N = BN / WARPS_N;
+
+  const int warpid = threadIdx.x / 32;
+  const int laneid = threadIdx.x % 32;
+  const int wm = warpid / WARPS_N;
+  const int wn = warpid % WARPS_N;
+  const int offset_m = wm * WARP_STEP_M;
+  const int offset_n = wn * WARP_STEP_N;
+
+  extern __shared__ char shmem[];
+  SharedTile<T, BM, BK>(&xs)[1] = *(SharedTile<T, BM, BK>(*)[1])(&shmem[0]);
+  SharedTile<T, BN, BK>(&ws)[1] =
+      *(SharedTile<T, BN, BK>(*)[1])(&shmem[1 * sizeof(T) * BM * BK]);
+
+  RegisterTile<float, BM / WARPS_M, BN / WARPS_N> C;
+  RegisterTile<T, BM / WARPS_M, 16> A;
+  RegisterTile<T, BN / WARPS_N, 16> B;
+
+  const int max_rows = M - blockIdx.y * BM;
+
+  x += blockIdx.y * BM * K;
+  w += blockIdx.x * BN * K / get_pack_factor<bits>();
+  scales += blockIdx.x * BN * K / group_size;
+  biases += blockIdx.x * BN * K / group_size;
+  y += blockIdx.y * BM * N + blockIdx.x * BN;
+
+  C.fill(0);
+
+  int tic = 0;
+  uint32_t base_addr_xs[1], base_addr_ws[1];
+  base_addr_xs[0] = __cvta_generic_to_shared(&xs[0].data[0]);
+  base_addr_ws[0] = __cvta_generic_to_shared(&ws[0].data[0]);
+
+  if (aligned_M || max_rows >= BM) {
+    for (int k_block = 0; k_block < K; k_block += BK) {
+      load_async<NUM_WARPS>(xs[tic], base_addr_xs[tic], x + k_block, K);
+      cp_async_commit();
+      load_quantized<NUM_WARPS, group_size, bits>(
+          ws[tic],
+          w + k_block / get_pack_factor<bits>(),
+          scales + k_block / group_size,
+          biases + k_block / group_size,
+          K);
+      cp_async_wait_all();
+      __syncthreads();
+
+      MLX_UNROLL
+      for (int k = 0; k < BK / 16; k++) {
+        A.load(
+            xs[tic],
+            base_addr_xs[tic],
+            offset_m + laneid % 16,
+            k * 16 + laneid / 16 * 8);
+        B.load(
+            ws[tic],
+            base_addr_ws[tic],
+            offset_n + laneid % 16,
+            k * 16 + laneid / 16 * 8);
+        mma_t(C, A, B);
+      }
+    }
+    C.store_global(y, N, offset_m, offset_n);
+  } else {
+    for (int k_block = 0; k_block < K; k_block += BK) {
+      load_async_safe<NUM_WARPS>(
+          xs[tic], base_addr_xs[tic], x + k_block, K, max_rows);
+      cp_async_commit();
+      load_quantized<NUM_WARPS, group_size, bits>(
+          ws[tic],
+          w + k_block / get_pack_factor<bits>(),
+          scales + k_block / group_size,
+          biases + k_block / group_size,
+          K);
+      cp_async_wait_all();
+      __syncthreads();
+
+      MLX_UNROLL
+      for (int k = 0; k < BK / 16; k++) {
+        A.load(
+            xs[tic],
+            base_addr_xs[tic],
+            offset_m + laneid % 16,
+            k * 16 + laneid / 16 * 8);
+        B.load(
+            ws[tic],
+            base_addr_ws[tic],
+            offset_n + laneid % 16,
+            k * 16 + laneid / 16 * 8);
+        mma_t(C, A, B);
+      }
+    }
+    C.store_global_safe(y, N, offset_m, offset_n, max_rows);
+  }
+}
+
+} // namespace cu
+
+void qmm(
+    const array& x,
+    const array& w,
+    const array& scales,
+    const array& biases,
+    array& out,
+    bool transpose_,
+    int group_size_,
+    int bits_,
+    int M,
+    int N,
+    int K,
+    cu::CommandEncoder& enc,
+    const Stream& s) {
+  if (x.dtype() != bfloat16) {
+    throw std::invalid_argument("[qmm] Only bfloat16 is supported for now");
+  }
+  if (!transpose_) {
+    throw std::invalid_argument(
+        "[qmm] Only transposed matmul is supported for now");
+  }
+
+  dispatch_float_types(x.dtype(), "qmm", [&](auto type_tag) {
+    dispatch_groups(group_size_, [&](auto group_size) {
+      dispatch_bits(bits_, [&](auto bits) {
+        using DataType = cuda_type_t<MLX_GET_TYPE(type_tag)>;
+
+        constexpr int BM = 128;
+        constexpr int BN = 128;
+        constexpr int BK = 32;
+        auto kernel =
+            cu::qmm_t<DataType, BM, BN, BK, group_size.value, bits.value, true>;
+        if (M % BM != 0) {
+          kernel = cu::
+              qmm_t<DataType, BM, BN, BK, group_size.value, bits.value, false>;
+        }
+
+        dim3 grid((N + BN - 1) / BN, (M + BM - 1) / BM);
+
+        enc.add_kernel_node(
+            kernel,
+            grid,
+            2 * 4 * 32,
+            1 * sizeof(DataType) * (BM * BK + BN * BK),
+            x.data<DataType>(),
+            w.data<uint8_t>(),
+            scales.data<DataType>(),
+            biases.data<DataType>(),
+            out.data<DataType>(),
+            M,
+            N,
+            K);
+      });
+    });
+  });
+}
+
+} // namespace mlx::core

mlx/backend/cuda/quantized/quantized.cu

@@ -0,0 +1,113 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/backend/cuda/device.h"
+#include "mlx/backend/cuda/kernel_utils.cuh"
+#include "mlx/backend/cuda/quantized/quantized.cuh"
+#include "mlx/backend/gpu/copy.h"
+#include "mlx/dtype_utils.h"
+#include "mlx/fast_primitives.h"
+
+#include <cooperative_groups.h>
+#include <cooperative_groups/reduce.h>
+#include <nvtx3/nvtx3.hpp>
+
+namespace mlx::core {
+
+namespace {
+
+inline array ensure_row_contiguous(
+    const array& x,
+    cu::CommandEncoder& enc,
+    const Stream& s) {
+  if (!x.flags().row_contiguous) {
+    array x_copy = contiguous_copy_gpu(x, s);
+    enc.add_temporary(x_copy);
+    return x_copy;
+  } else {
+    return x;
+  }
+}
+
+inline array ensure_row_contiguous_matrix(
+    const array& x,
+    cu::CommandEncoder& enc,
+    const Stream& s) {
+  auto stride_0 = x.strides()[x.ndim() - 2];
+  auto stride_1 = x.strides()[x.ndim() - 1];
+  if (stride_0 == x.shape(-1) && stride_1 == 1) {
+    return x;
+  } else {
+    array x_copy = contiguous_copy_gpu(x, s);
+    enc.add_temporary(x_copy);
+    return x_copy;
+  }
+}
+
+} // namespace
+
+void QuantizedMatmul::eval_gpu(const std::vector<array>& inputs, array& out) {
+  auto& s = stream();
+  auto& d = cu::device(s.device);
+  auto& enc = d.get_command_encoder(s);
+
+  out.set_data(allocator::malloc(out.nbytes()));
+
+  // Make sure the last two dims of x and w, s, b are contiguous. This should
+  // be relaxed for x.
+  array x = ensure_row_contiguous_matrix(inputs[0], enc, s);
+  array w = ensure_row_contiguous_matrix(inputs[1], enc, s);
+  array scales = ensure_row_contiguous_matrix(inputs[2], enc, s);
+  array biases = ensure_row_contiguous_matrix(inputs[3], enc, s);
+
+  // Extract the matmul shapes
+  bool non_batched = w.ndim() == 2 && x.flags().row_contiguous;
+  int K = x.shape(-1);
+  int M = non_batched ? x.size() / K : x.shape(-2);
+  int N = out.shape(-1);
+
+  qmm(x,
+      w,
+      scales,
+      biases,
+      out,
+      transpose_,
+      group_size_,
+      bits_,
+      M,
+      N,
+      K,
+      enc,
+      s);
+}
+
+void fast::AffineQuantize::eval_gpu(
+    const std::vector<array>& inputs,
+    std::vector<array>& outputs) {
+  auto& s = stream();
+  auto& d = cu::device(s.device);
+  auto& enc = d.get_command_encoder(s);
+
+  if (dequantize_) {
+    auto wq = ensure_row_contiguous(inputs[0], enc, s);
+    auto scales = ensure_row_contiguous(inputs[1], enc, s);
+    auto biases = ensure_row_contiguous(inputs[2], enc, s);
+    auto& w = outputs[0];
+
+    w.set_data(allocator::malloc(w.nbytes()));
+
+    affine_dequantize(wq, scales, biases, w, group_size_, bits_, enc, s);
+  } else {
+    auto w = ensure_row_contiguous(inputs[0], enc, s);
+    auto& wq = outputs[0];
+    auto& scales = outputs[1];
+    auto& biases = outputs[2];
+
+    wq.set_data(allocator::malloc(wq.nbytes()));
+    scales.set_data(allocator::malloc(scales.nbytes()));
+    biases.set_data(allocator::malloc(biases.nbytes()));
+
+    affine_quantize(w, wq, scales, biases, group_size_, bits_, enc, s);
+  }
+}
+
+} // namespace mlx::core

mlx/backend/cuda/quantized/quantized.cuh

@@ -0,0 +1,42 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/backend/cuda/device.h"
+
+namespace mlx::core {
+
+void affine_quantize(
+    const array& w,
+    array& wq,
+    array& scales,
+    array& biases,
+    int group_size_,
+    int bits_,
+    cu::CommandEncoder& enc,
+    const Stream& s);
+
+void affine_dequantize(
+    const array& wq,
+    const array& scales,
+    const array& biases,
+    array& w,
+    int group_size_,
+    int bits_,
+    cu::CommandEncoder& enc,
+    const Stream& s);
+
+void qmm(
+    const array& x,
+    const array& w,
+    const array& scales,
+    const array& biases,
+    array& out,
+    bool transpose_,
+    int group_size_,
+    int bits_,
+    int M,
+    int N,
+    int K,
+    cu::CommandEncoder& enc,
+    const Stream& s);
+
+} // namespace mlx::core

mlx/backend/cuda/quantized/quantized_utils.cuh

@@ -0,0 +1,59 @@
+// Copyright © 2025 Apple Inc.
+
+namespace mlx::core {
+
+namespace cu {
+
+template <int bits, int wsize = 8>
+inline constexpr __device__ short get_pack_factor() {
+  return (bits == 3 || bits == 5) ? 8 : (bits == 6 ? 4 : wsize / bits);
+}
+
+template <int bits, int wsize = 8>
+inline constexpr __device__ short get_bytes_per_pack() {
+  constexpr int power_of_2_bits = (bits & (bits - 1)) == 0;
+  return power_of_2_bits ? (wsize / 8) : (bits == 5 ? 5 : 3);
+}
+
+} // namespace cu
+
+template <typename F>
+void dispatch_groups(int group_size, F&& f) {
+  switch (group_size) {
+    case 32:
+      f(std::integral_constant<int, 32>{});
+      break;
+    case 64:
+      f(std::integral_constant<int, 64>{});
+      break;
+    case 128:
+      f(std::integral_constant<int, 128>{});
+      break;
+  }
+}
+
+template <typename F>
+void dispatch_bits(int bits, F&& f) {
+  switch (bits) {
+    case 2:
+      f(std::integral_constant<int, 2>{});
+      break;
+    case 3:
+      f(std::integral_constant<int, 3>{});
+      break;
+    case 4:
+      f(std::integral_constant<int, 4>{});
+      break;
+    case 5:
+      f(std::integral_constant<int, 5>{});
+      break;
+    case 6:
+      f(std::integral_constant<int, 6>{});
+      break;
+    case 8:
+      f(std::integral_constant<int, 8>{});
+      break;
+  }
+}
+
+} // namespace mlx::core

mlx/backend/cuda/random.cu

@@ -170,6 +170,7 @@ void RandomBits::eval_gpu(const std::vector<array>& inputs, array& out) {
         cu::rbitsc,
         grid,
         block,
+        0,
         keys.data<uint32_t>(),
         out.data<uint8_t>(),
         grid_dims,
@@ -180,6 +181,7 @@ void RandomBits::eval_gpu(const std::vector<array>& inputs, array& out) {
         cu::rbits,
         grid,
         block,
+        0,
         keys.data<uint32_t>(),
         out.data<uint8_t>(),
         grid_dims,

mlx/backend/cuda/reduce.cu

@@ -47,8 +47,7 @@ void Reduce::eval_gpu(const std::vector<array>& inputs, array& out) {
     }
   }
   if (plan.type == GeneralReduce || broadcasted || !in.flags().contiguous) {
-    array in_copy(in.shape(), in.dtype(), nullptr, {});
-    copy_gpu(in, in_copy, CopyType::General, s);
+    array in_copy = contiguous_copy_gpu(in, s);
     encoder.add_temporary(in_copy);
     in = in_copy;
     plan = get_reduction_plan(in, axes_);

mlx/backend/cuda/reduce/all_reduce.cu

@@ -37,15 +37,15 @@ __global__ void all_reduce(T* in, U* out, size_t block_step, size_t size) {
   for (; i + block.size() * N <= check; i += block.size() * N) {
     cub::LoadDirectBlockedVectorized<T, N>(block.thread_rank(), in + i, vals);
     for (int j = 0; j < N; j++) {
-      accs[0] = op(accs[0], __cast<U, T>(vals[j]));
+      accs[0] = op(accs[0], cast_to<U>(vals[j]));
     }
   }
 
   if (i < check) {
     cub::LoadDirectBlocked(
-        block.thread_rank(), in + i, vals, check - i, __cast<T, U>(init));
+        block.thread_rank(), in + i, vals, check - i, cast_to<T>(init));
     for (int i = 0; i < N; i++) {
-      accs[0] = op(accs[0], __cast<U, T>(vals[i]));
+      accs[0] = op(accs[0], cast_to<U>(vals[i]));
     }
   }
 
@@ -120,6 +120,7 @@ void all_reduce(
             kernel,
             blocks,
             threads,
+            0,
             static_cast<T*>(indata),
             intermediate.data<U>(),
             block_step,
@@ -146,6 +147,7 @@ void all_reduce(
           kernel,
           blocks,
           threads,
+          0,
           static_cast<T*>(indata),
           out.data<U>(),
           block_step,

mlx/backend/cuda/reduce/col_reduce.cu

@@ -3,7 +3,6 @@
 #include <numeric>
 
 #include "mlx/backend/cuda/device.h"
-#include "mlx/backend/cuda/device/cast_op.cuh"
 #include "mlx/backend/cuda/reduce/reduce.cuh"
 
 #include <cooperative_groups.h>
@@ -128,7 +127,7 @@ col_reduce_looped(T* in, U* out, const __grid_constant__ ColReduceArgs args) {
         T vals[N_READS];
         cub::LoadDirectBlockedVectorized(thread_x, in + loop.location(), vals);
         for (int i = 0; i < N_READS; i++) {
-          totals[i] = op(totals[i], __cast<U, T>(vals[i]));
+          totals[i] = op(totals[i], cast_to<U>(vals[i]));
         }
         loop.next(BM, args.reduce_shape.data(), args.reduce_strides.data());
       }
@@ -137,7 +136,7 @@ col_reduce_looped(T* in, U* out, const __grid_constant__ ColReduceArgs args) {
         T vals[N_READS];
         cub::LoadDirectBlocked(thread_x, in + loop.location(), vals);
         for (int i = 0; i < N_READS; i++) {
-          totals[i] = op(totals[i], __cast<U, T>(vals[i]));
+          totals[i] = op(totals[i], cast_to<U>(vals[i]));
         }
         loop.next(BM, args.reduce_shape.data(), args.reduce_strides.data());
       }
@@ -150,9 +149,9 @@ col_reduce_looped(T* in, U* out, const __grid_constant__ ColReduceArgs args) {
           in + loop.location(),
           vals,
           args.reduction_stride - tile_x * BN,
-          __cast<T, U>(ReduceInit<Op, T>::value()));
+          cast_to<T>(ReduceInit<Op, T>::value()));
       for (int i = 0; i < N_READS; i++) {
-        totals[i] = op(totals[i], __cast<U, T>(vals[i]));
+        totals[i] = op(totals[i], cast_to<U>(vals[i]));
       }
       loop.next(BM, args.reduce_shape.data(), args.reduce_strides.data());
     }
@@ -231,7 +230,7 @@ void col_reduce_looped(
         auto kernel =
             cu::col_reduce_looped<T, U, OP, reduce_ndim(), BM, BN, N_READS>;
         encoder.add_kernel_node(
-            kernel, grid, blocks, indata, out.data<U>(), args);
+            kernel, grid, blocks, 0, indata, out.data<U>(), args);
       });
     });
   });

mlx/backend/cuda/reduce/init_reduce.cu

@@ -41,7 +41,8 @@ void init_reduce(
       dim3 grid = get_2d_grid_dims(out.shape(), out.strides());
       dim3 block(grid.x < 1024 ? grid.x : 1024, 1, 1);
       grid.x = (grid.x + 1023) / 1024;
-      encoder.add_kernel_node(kernel, grid, block, out.data<U>(), out.size());
+      encoder.add_kernel_node(
+          kernel, grid, block, 0, out.data<U>(), out.size());
     });
   });
 }

mlx/backend/cuda/reduce/reduce.cuh

@@ -3,7 +3,6 @@
 #include <type_traits>
 
 #include "mlx/backend/common/reduce.h"
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
 #include "mlx/backend/cuda/kernel_utils.cuh"
 #include "mlx/backend/cuda/reduce/reduce_ops.cuh"
 #include "mlx/dtype_utils.h"

mlx/backend/cuda/reduce/reduce_ops.cuh

@@ -2,6 +2,8 @@
 
 #pragma once
 
+#include "mlx/backend/cuda/device/atomic_ops.cuh"
+#include "mlx/backend/cuda/device/cast_op.cuh"
 #include "mlx/backend/cuda/device/utils.cuh"
 #include "mlx/backend/cuda/reduce/reduce_utils.cuh"
 
@@ -40,15 +42,15 @@ struct Sum {
   }
 
   __device__ void atomic_update(__nv_bfloat16* x, __nv_bfloat16 y) {
-    atomicAdd(x, y);
+    atomic_add(x, y);
   }
 
   __device__ void atomic_update(int* x, int y) {
-    atomicAdd(x, y);
+    atomic_add(x, y);
   }
 
   __device__ void atomic_update(float* x, float y) {
-    atomicAdd(x, y);
+    atomic_add(x, y);
   }
 };
 
@@ -67,6 +69,18 @@ struct Prod {
 struct Min {
   template <typename T>
   __device__ __forceinline__ T operator()(T a, T b) {
+    if constexpr (is_complex_v<T>) {
+      if (isnan(a.real()) || isnan(a.imag())) {
+        return a;
+      }
+      if (isnan(b.real()) || isnan(b.imag())) {
+        return b;
+      }
+    } else if constexpr (!cuda::std::is_integral_v<T>) {
+      if (isnan(a) || isnan(b)) {
+        return cuda::std::numeric_limits<float>::quiet_NaN();
+      }
+    }
     return a < b ? a : b;
   }
 
@@ -79,6 +93,18 @@ struct Min {
 struct Max {
   template <typename T>
   __device__ __forceinline__ T operator()(T a, T b) {
+    if constexpr (is_complex_v<T>) {
+      if (isnan(a.real()) || isnan(a.imag())) {
+        return a;
+      }
+      if (isnan(b.real()) || isnan(b.imag())) {
+        return b;
+      }
+    } else if constexpr (!cuda::std::is_integral_v<T>) {
+      if (isnan(a) || isnan(b)) {
+        return cuda::std::numeric_limits<float>::quiet_NaN();
+      }
+    }
     return a > b ? a : b;
   }
 
@@ -149,10 +175,10 @@ struct ReduceInit<Or, T> {
 template <typename T>
 struct ReduceInit<Sum, T> {
   static constexpr __host__ __device__ auto value() {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
+    if constexpr (is_complex_v<T>) {
       return T{0, 0};
     } else {
-      return typename ReduceResult<Sum, T>::type{0};
+      return cast_to<typename ReduceResult<Sum, T>::type>(0);
     }
   }
 };
@@ -160,10 +186,10 @@ struct ReduceInit<Sum, T> {
 template <typename T>
 struct ReduceInit<Prod, T> {
   static constexpr __host__ __device__ auto value() {
-    if constexpr (cuda::std::is_same_v<T, cuComplex>) {
+    if constexpr (is_complex_v<T>) {
       return T{1, 0};
     } else {
-      return typename ReduceResult<Prod, T>::type{1};
+      return cast_to<typename ReduceResult<Prod, T>::type>(1);
     }
   }
 };

mlx/backend/cuda/reduce/reduce_utils.cuh

@@ -4,6 +4,7 @@
 
 #include <numeric>
 
+#include "mlx/backend/common/utils.h"
 #include "mlx/backend/cuda/device/utils.cuh"
 
 #include <cooperative_groups.h>
@@ -55,22 +56,6 @@ __device__ void atomic_reduce(T* x, T y) {
   }
 }
 
-// TODO: Should make a custom complex type
-template <typename U, typename T>
-inline __device__ U __cast(T x) {
-  return static_cast<U>(x);
-}
-
-template <>
-inline __device__ bool __cast<bool, cuComplex>(cuComplex x) {
-  return x.x != 0 && x.y != 0;
-}
-
-template <>
-inline __device__ cuComplex __cast<cuComplex, bool>(bool x) {
-  return x ? make_cuFloatComplex(1, 1) : make_cuFloatComplex(0, 0);
-}
-
 template <typename T, int N, typename Block, typename Warp, typename Op>
 inline __device__ void
 block_reduce(Block block, Warp warp, T (&vals)[N], T* smem, Op op, T init) {

mlx/backend/cuda/reduce/row_reduce.cu

@@ -3,7 +3,6 @@
 #include <numeric>
 
 #include "mlx/backend/cuda/device.h"
-#include "mlx/backend/cuda/device/cast_op.cuh"
 #include "mlx/backend/cuda/reduce/reduce.cuh"
 
 #include <cooperative_groups.h>
@@ -113,7 +112,7 @@ __global__ void row_reduce_simple(T* in, U* out, size_t n_rows, int size) {
             in + k * size + r * (block.size() * N),
             vals[k]);
         for (int j = 0; j < N; j++) {
-          accs[k] = op(accs[k], __cast<U, T>(vals[k][j]));
+          accs[k] = op(accs[k], cast_to<U>(vals[k][j]));
         }
       }
     }
@@ -125,7 +124,7 @@ __global__ void row_reduce_simple(T* in, U* out, size_t n_rows, int size) {
             in + k * size + r * (block.size() * N),
             vals[k]);
         for (int j = 0; j < N; j++) {
-          accs[k] = op(accs[k], __cast<U, T>(vals[k][j]));
+          accs[k] = op(accs[k], cast_to<U>(vals[k][j]));
         }
       }
     }
@@ -138,9 +137,9 @@ __global__ void row_reduce_simple(T* in, U* out, size_t n_rows, int size) {
           in + k * size + final_offset,
           vals[k],
           size,
-          __cast<T, U>(init));
+          cast_to<T>(init));
       for (int j = 0; j < N; j++) {
-        accs[k] = op(accs[k], __cast<U, T>(vals[k][j]));
+        accs[k] = op(accs[k], cast_to<U>(vals[k][j]));
       }
     }
   }
@@ -199,7 +198,7 @@ __global__ void row_reduce_looped(
           in + loop.location() + r * BLOCK_DIM * N_READS,
           vals);
       for (int i = 0; i < N_READS; i++) {
-        total[0] = op(total[0], __cast<U, T>(vals[i]));
+        total[0] = op(total[0], cast_to<U>(vals[i]));
       }
     }
     if (final_offset < args.row_size) {
@@ -209,9 +208,9 @@ __global__ void row_reduce_looped(
           in + loop.location() + final_offset,
           vals,
           args.row_size - final_offset,
-          __cast<T, U>(init));
+          cast_to<T>(init));
       for (int i = 0; i < N_READS; i++) {
-        total[0] = op(total[0], __cast<U, T>(vals[i]));
+        total[0] = op(total[0], cast_to<U>(vals[i]));
       }
     }
     // TODO: Maybe block.sync() here?
@@ -270,7 +269,7 @@ void row_reduce_simple(
 
       int size = plan.shape.back();
       encoder.add_kernel_node(
-          kernel, grid, block, indata, out.data<U>(), out.size(), size);
+          kernel, grid, block, 0, indata, out.data<U>(), out.size(), size);
     });
   });
 }
@@ -323,7 +322,7 @@ void row_reduce_looped(
       });
 
       encoder.add_kernel_node(
-          kernel, grid, block, indata, out.data<U>(), out.size(), args);
+          kernel, grid, block, 0, indata, out.data<U>(), out.size(), args);
     });
   });
 }

mlx/backend/cuda/rms_norm.cu

@@ -74,7 +74,7 @@ __global__ void rms_norm(
   for (int r = 0; r < cuda::ceil_div(axis_size, BLOCK_DIM * N_READS); ++r) {
     auto index = r * BLOCK_DIM + block.thread_rank();
     T xn[N_READS];
-    cub::LoadDirectBlocked(index, x, xn, axis_size, 0);
+    cub::LoadDirectBlocked(index, x, xn, axis_size, cast_to<T>(0));
     for (int i = 0; i < N_READS; ++i) {
       float t = static_cast<float>(xn[i]);
       normalizer += t * t;
@@ -130,7 +130,7 @@ __global__ void rms_norm_vjp(
     T wn[N_READS] = {};
     T gn[N_READS] = {};
     auto index = r * BLOCK_DIM + block.thread_rank();
-    cub::LoadDirectBlocked(index, x, xn, axis_size, 0);
+    cub::LoadDirectBlocked(index, x, xn, axis_size, cast_to<T>(0));
     cub::LoadDirectBlocked(index, g, gn, axis_size);
     cub::LoadDirectBlocked(index, strided_iterator(w, w_stride), wn, axis_size);
     for (int i = 0; i < N_READS; i++) {
@@ -206,8 +206,7 @@ void RMSNorm::eval_gpu(
       }
       return x;
     } else {
-      auto x_copy = array(x.shape(), x.dtype(), nullptr, {});
-      copy_gpu(x, x_copy, CopyType::General, s);
+      array x_copy = contiguous_copy_gpu(x, s);
       out.copy_shared_buffer(x_copy);
       return x_copy;
     }
@@ -233,6 +232,7 @@ void RMSNorm::eval_gpu(
           kernel,
           n_rows,
           block_dim(),
+          0,
           x.data<DataType>(),
           w.data<DataType>(),
           out.data<DataType>(),
@@ -259,9 +259,7 @@ void RMSNormVJP::eval_gpu(
       return x;
     }
     copied = true;
-    array x_copy(x.shape(), x.dtype(), nullptr, {});
-    copy_gpu(x, x_copy, CopyType::General, s);
-    return x_copy;
+    return contiguous_copy_gpu(x, s);
   };
   bool donate_x = inputs[0].is_donatable();
   bool donate_g = inputs[2].is_donatable();
@@ -330,6 +328,7 @@ void RMSNormVJP::eval_gpu(
                 kernel,
                 n_rows,
                 block_dim(),
+                0,
                 x.data<DataType>(),
                 w.data<DataType>(),
                 g.data<DataType>(),

mlx/backend/cuda/rope.cu

@@ -325,6 +325,7 @@ void RoPE::eval_gpu(
               kernel,
               grid,
               block,
+              0,
               (donated ? out : in).data<DataType>(),
               out.data<DataType>(),
               offset.data<int32_t>(),
@@ -341,6 +342,7 @@ void RoPE::eval_gpu(
               kernel,
               grid,
               block,
+              0,
               (donated ? out : in).data<DataType>(),
               out.data<DataType>(),
               offset.data<int32_t>(),
@@ -360,6 +362,7 @@ void RoPE::eval_gpu(
               kernel,
               grid,
               block,
+              0,
               (donated ? out : in).data<DataType>(),
               out.data<DataType>(),
               offset.data<int32_t>(),
@@ -381,6 +384,7 @@ void RoPE::eval_gpu(
               kernel,
               grid,
               block,
+              0,
               (donated ? out : in).data<DataType>(),
               out.data<DataType>(),
               offset.data<int32_t>(),

mlx/backend/cuda/scan.cu

@@ -0,0 +1,467 @@
+// Copyright © 2025 Apple Inc.
+
+#include "mlx/backend/cuda/device.h"
+#include "mlx/backend/cuda/device/binary_ops.cuh"
+#include "mlx/backend/cuda/kernel_utils.cuh"
+#include "mlx/backend/cuda/reduce/reduce_ops.cuh"
+#include "mlx/backend/gpu/copy.h"
+#include "mlx/dtype_utils.h"
+#include "mlx/primitives.h"
+
+#include <cooperative_groups.h>
+#include <cooperative_groups/scan.h>
+#include <nvtx3/nvtx3.hpp>
+
+#include <cassert>
+
+namespace mlx::core {
+
+namespace cu {
+
+namespace cg = cooperative_groups;
+
+template <typename Op, typename T>
+struct ScanResult {
+  using type = T;
+};
+
+template <>
+struct ScanResult<Sum, bool> {
+  using type = int32_t;
+};
+
+template <typename T>
+struct ReduceInit<LogAddExp, T> {
+  static constexpr __host__ __device__ T value() {
+    return Limits<T>::min();
+  }
+};
+
+template <bool reverse, typename T, typename U, int N_READS>
+inline __device__ void
+load_values(int index, const T* in, U (&values)[N_READS], int size, U init) {
+  int remaining = size - index * N_READS;
+  if constexpr (reverse) {
+    in += remaining - N_READS;
+    if (remaining < N_READS) {
+      for (int i = 0; i < N_READS; ++i) {
+        values[N_READS - i - 1] =
+            (N_READS - i - 1 < remaining) ? cast_to<U>(in[i]) : init;
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        values[N_READS - i - 1] = cast_to<U>(in[i]);
+      }
+    }
+  } else {
+    in += index * N_READS;
+    if (remaining < N_READS) {
+      for (int i = 0; i < N_READS; ++i) {
+        values[i] = (i < remaining) ? cast_to<U>(in[i]) : init;
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        values[i] = cast_to<U>(in[i]);
+      }
+    }
+  }
+}
+
+template <bool reverse, int offset, typename T, int N_READS>
+inline __device__ void
+store_values(int index, T* out, T (&values)[N_READS], int size) {
+  int start = index * N_READS + offset;
+  int remaining = size - start;
+  if constexpr (reverse) {
+    out += remaining - N_READS;
+    if (remaining < N_READS) {
+      for (int i = 0; i < N_READS; ++i) {
+        if (N_READS - i - 1 < remaining) {
+          out[i] = values[N_READS - i - 1];
+        }
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        out[i] = values[N_READS - i - 1];
+      }
+    }
+  } else {
+    out += start;
+    if (remaining < N_READS) {
+      for (int i = 0; i < N_READS; ++i) {
+        if (i < remaining) {
+          out[i] = values[i];
+        }
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        out[i] = values[i];
+      }
+    }
+  }
+}
+
+template <
+    typename T,
+    typename U,
+    typename Op,
+    int N_READS,
+    bool inclusive,
+    bool reverse>
+__global__ void contiguous_scan(const T* in, U* out, int32_t axis_size) {
+  auto grid = cg::this_grid();
+  auto block = cg::this_thread_block();
+  auto warp = cg::tiled_partition<WARP_SIZE>(block);
+
+  in += grid.block_rank() * axis_size;
+  out += grid.block_rank() * axis_size;
+
+  __shared__ U warp_sums[WARP_SIZE];
+
+  Op op;
+  U init = ReduceInit<Op, T>::value();
+  U prefix = init;
+
+  // Scan per block.
+  for (int r = 0; r < cuda::ceil_div(axis_size, block.size() * N_READS); ++r) {
+    int32_t index = r * block.size() + block.thread_rank();
+    U values[N_READS];
+    load_values<reverse>(index, in, values, axis_size, init);
+
+    // Compute an inclusive scan per thread.
+    for (int i = 1; i < N_READS; ++i) {
+      values[i] = op(values[i], values[i - 1]);
+    }
+
+    // Compute exclusive scan of thread sums.
+    U prev_thread_sum = cg::exclusive_scan(warp, values[N_READS - 1], op);
+    if (warp.thread_rank() == 0) {
+      prev_thread_sum = init;
+    }
+
+    // Write wrap's sum to shared memory.
+    if (warp.thread_rank() == WARP_SIZE - 1) {
+      warp_sums[warp.meta_group_rank()] =
+          op(prev_thread_sum, values[N_READS - 1]);
+    }
+    block.sync();
+
+    // Compute exclusive scan of warp sums.
+    if (warp.meta_group_rank() == 0) {
+      U prev_warp_sum =
+          cg::exclusive_scan(warp, warp_sums[warp.thread_rank()], op);
+      if (warp.thread_rank() == 0) {
+        prev_warp_sum = init;
+      }
+      warp_sums[warp.thread_rank()] = prev_warp_sum;
+    }
+    block.sync();
+
+    // Compute the output.
+    for (int i = 0; i < N_READS; ++i) {
+      values[i] = op(values[i], prefix);
+      values[i] = op(values[i], warp_sums[warp.meta_group_rank()]);
+      values[i] = op(values[i], prev_thread_sum);
+    }
+
+    // Write the values.
+    if (inclusive) {
+      store_values<reverse, 0>(index, out, values, axis_size);
+    } else {
+      store_values<reverse, 1>(index, out, values, axis_size);
+      if (reverse) {
+        if (block.thread_rank() == 0 && index == 0) {
+          out[axis_size - 1] = init;
+        }
+      } else {
+        if (block.thread_rank() == 0 && index == 0) {
+          out[0] = init;
+        }
+      }
+    }
+    block.sync();
+
+    // Share the prefix.
+    if ((warp.meta_group_rank() == warp.meta_group_size() - 1) &&
+        (warp.thread_rank() == WARP_SIZE - 1)) {
+      warp_sums[0] = values[N_READS - 1];
+    }
+    block.sync();
+    prefix = warp_sums[0];
+  }
+}
+
+template <
+    typename T,
+    typename U,
+    typename Op,
+    int N_READS,
+    int BM,
+    int BN,
+    bool inclusive,
+    bool reverse>
+__global__ void strided_scan(
+    const T* in,
+    U* out,
+    int32_t axis_size,
+    int64_t stride,
+    int64_t stride_blocks) {
+  auto grid = cg::this_grid();
+  auto block = cg::this_thread_block();
+  auto warp = cg::tiled_partition<WARP_SIZE>(block);
+
+  constexpr int BN_pad = WARP_SIZE + 16 / sizeof(U);
+  constexpr int n_warps = BN / N_READS;
+  constexpr int n_scans = BN / n_warps;
+
+  __shared__ U read_buffer[BM * BN_pad];
+
+  Op op;
+  U init = ReduceInit<Op, T>::value();
+  U values[n_scans];
+  U prefix[n_scans];
+  for (int i = 0; i < n_scans; ++i) {
+    prefix[i] = init;
+  }
+
+  // Compute offsets.
+  int64_t offset = (grid.block_rank() / stride_blocks) * axis_size * stride;
+  int64_t global_index_x = (grid.block_rank() % stride_blocks) * BN;
+  uint read_offset_y = (block.thread_rank() * N_READS) / BN;
+  uint read_offset_x = (block.thread_rank() * N_READS) % BN;
+  uint scan_offset_y = warp.thread_rank();
+  uint scan_offset_x = warp.meta_group_rank() * n_scans;
+
+  uint stride_limit = stride - global_index_x;
+  in += offset + global_index_x + read_offset_x;
+  out += offset + global_index_x + read_offset_x;
+  U* read_into = read_buffer + read_offset_y * BN_pad + read_offset_x;
+  U* read_from = read_buffer + scan_offset_y * BN_pad + scan_offset_x;
+
+  for (uint j = 0; j < axis_size; j += BM) {
+    // Calculate the indices for the current thread.
+    uint index_y = j + read_offset_y;
+    uint check_index_y = index_y;
+    if (reverse) {
+      index_y = axis_size - 1 - index_y;
+    }
+
+    // Read in SM.
+    if (check_index_y < axis_size && (read_offset_x + N_READS) < stride_limit) {
+      for (int i = 0; i < N_READS; ++i) {
+        read_into[i] = in[index_y * stride + i];
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        if (check_index_y < axis_size && (read_offset_x + i) < stride_limit) {
+          read_into[i] = in[index_y * stride + i];
+        } else {
+          read_into[i] = init;
+        }
+      }
+    }
+    block.sync();
+
+    // Read strided into registers.
+    for (int i = 0; i < n_scans; ++i) {
+      values[i] = read_from[i];
+    }
+
+    // Perform the scan.
+    for (int i = 0; i < n_scans; ++i) {
+      values[i] = cg::inclusive_scan(warp, values[i], op);
+      values[i] = op(values[i], prefix[i]);
+      prefix[i] = warp.shfl(values[i], WARP_SIZE - 1);
+    }
+
+    // Write to SM.
+    for (int i = 0; i < n_scans; ++i) {
+      read_from[i] = values[i];
+    }
+    block.sync();
+
+    // Write to device memory.
+    if (!inclusive) {
+      if (check_index_y == 0) {
+        if ((read_offset_x + N_READS) < stride_limit) {
+          for (int i = 0; i < N_READS; ++i) {
+            out[index_y * stride + i] = init;
+          }
+        } else {
+          for (int i = 0; i < N_READS; ++i) {
+            if ((read_offset_x + i) < stride_limit) {
+              out[index_y * stride + i] = init;
+            }
+          }
+        }
+      }
+      if (reverse) {
+        index_y -= 1;
+        check_index_y += 1;
+      } else {
+        index_y += 1;
+        check_index_y += 1;
+      }
+    }
+    if (check_index_y < axis_size && (read_offset_x + N_READS) < stride_limit) {
+      for (int i = 0; i < N_READS; ++i) {
+        out[index_y * stride + i] = read_into[i];
+      }
+    } else {
+      for (int i = 0; i < N_READS; ++i) {
+        if (check_index_y < axis_size && (read_offset_x + i) < stride_limit) {
+          out[index_y * stride + i] = read_into[i];
+        }
+      }
+    }
+  }
+}
+
+} // namespace cu
+
+template <typename F>
+void dispatch_scan_ops(Scan::ReduceType scan_op, F&& f) {
+  if (scan_op == Scan::ReduceType::Max) {
+    f(type_identity<cu::Max>{});
+  } else if (scan_op == Scan::ReduceType::Min) {
+    f(type_identity<cu::Min>{});
+  } else if (scan_op == Scan::ReduceType::Sum) {
+    f(type_identity<cu::Sum>{});
+  } else if (scan_op == Scan::ReduceType::Prod) {
+    f(type_identity<cu::Prod>{});
+  } else if (scan_op == Scan::ReduceType::LogAddExp) {
+    f(type_identity<cu::LogAddExp>{});
+  } else {
+    throw std::invalid_argument("Unknown reduce type.");
+  }
+}
+
+template <typename Op>
+const char* op_to_string() {
+  if (cuda::std::is_same_v<Op, cu::Max>) {
+    return "Max";
+  } else if (cuda::std::is_same_v<Op, cu::Min>) {
+    return "Min";
+  } else if (cuda::std::is_same_v<Op, cu::Sum>) {
+    return "Sum";
+  } else if (cuda::std::is_same_v<Op, cu::Prod>) {
+    return "Prod";
+  } else if (cuda::std::is_same_v<Op, cu::LogAddExp>) {
+    return "LogAddExp";
+  } else {
+    throw std::invalid_argument("Unknown op.");
+  }
+}
+
+template <typename Op, typename T>
+constexpr bool supports_scan_op() {
+  if constexpr (cuda::std::is_same_v<Op, LogAddExp>) {
+    return is_inexact_v<T>;
+  } else {
+    return true;
+  }
+}
+
+void Scan::eval_gpu(const std::vector<array>& inputs, array& out) {
+  nvtx3::scoped_range r("Scan::eval_gpu");
+  assert(inputs.size() == 1);
+  auto in = inputs[0];
+  auto& s = stream();
+
+  if (in.flags().contiguous && in.strides()[axis_] != 0) {
+    if (in.is_donatable() && in.itemsize() == out.itemsize()) {
+      out.copy_shared_buffer(in);
+    } else {
+      out.set_data(
+          allocator::malloc(in.data_size() * out.itemsize()),
+          in.data_size(),
+          in.strides(),
+          in.flags());
+    }
+  } else {
+    in = contiguous_copy_gpu(in, s);
+    out.copy_shared_buffer(in);
+  }
+
+  constexpr int N_READS = 4;
+  int32_t axis_size = in.shape(axis_);
+  bool contiguous = in.strides()[axis_] == 1;
+
+  auto& encoder = cu::get_command_encoder(s);
+  encoder.set_input_array(in);
+  encoder.set_output_array(out);
+
+  dispatch_all_types(in.dtype(), [&](auto type_tag) {
+    using T = cuda_type_t<MLX_GET_TYPE(type_tag)>;
+    dispatch_scan_ops(reduce_type_, [&](auto scan_op_tag) {
+      using Op = MLX_GET_TYPE(scan_op_tag);
+      if constexpr (supports_scan_op<Op, T>) {
+        using U = typename cu::ScanResult<Op, T>::type;
+        dispatch_bool(inclusive_, [&](auto inclusive) {
+          dispatch_bool(reverse_, [&](auto reverse) {
+            if (contiguous) {
+              auto kernel = cu::contiguous_scan<
+                  T,
+                  U,
+                  Op,
+                  N_READS,
+                  inclusive.value,
+                  reverse.value>;
+              int block_dim = cuda::ceil_div(axis_size, N_READS);
+              block_dim = cuda::ceil_div(block_dim, WARP_SIZE) * WARP_SIZE;
+              block_dim = std::min(block_dim, WARP_SIZE * WARP_SIZE);
+              encoder.add_kernel_node(
+                  kernel,
+                  in.data_size() / axis_size,
+                  block_dim,
+                  0,
+                  in.data<T>(),
+                  out.data<U>(),
+                  axis_size);
+            } else {
+              constexpr int BM = WARP_SIZE;
+              constexpr int BN = WARP_SIZE;
+              auto kernel = cu::strided_scan<
+                  T,
+                  U,
+                  Op,
+                  N_READS,
+                  BM,
+                  BN,
+                  inclusive.value,
+                  reverse.value>;
+              int64_t stride = in.strides()[axis_];
+              int64_t stride_blocks = cuda::ceil_div(stride, BN);
+              dim3 num_blocks = get_2d_grid_dims(
+                  in.shape(), in.strides(), axis_size * stride);
+              if (num_blocks.x * stride_blocks <= UINT32_MAX) {
+                num_blocks.x *= stride_blocks;
+              } else {
+                num_blocks.y *= stride_blocks;
+              }
+              int block_dim = (BN / N_READS) * WARP_SIZE;
+              encoder.add_kernel_node(
+                  kernel,
+                  num_blocks,
+                  block_dim,
+                  0,
+                  in.data<T>(),
+                  out.data<U>(),
+                  axis_size,
+                  stride,
+                  stride_blocks);
+            }
+          });
+        });
+      } else {
+        throw std::runtime_error(fmt::format(
+            "Can not do scan op {} on inputs of {} with result of {}.",
+            op_to_string<Op>(),
+            dtype_to_string(in.dtype()),
+            dtype_to_string(out.dtype())));
+      }
+    });
+  });
+}
+
+} // namespace mlx::core

mlx/backend/cuda/softmax.cu

@@ -43,7 +43,7 @@ __global__ void softmax(const T* in, T* out, int axis_size) {
   // Thread reduce.
   AccT prevmax;
   AccT maxval = Limits<AccT>::finite_min();
-  AccT normalizer = 0;
+  AccT normalizer = cast_to<AccT>(0);
   for (int r = 0; r < cuda::ceil_div(axis_size, BLOCK_DIM * N_READS); r++) {
     AccT vals[N_READS];
     cub::LoadDirectBlocked(
@@ -125,8 +125,7 @@ void Softmax::eval_gpu(const std::vector<array>& inputs, array& out) {
       }
       return x;
     } else {
-      auto x_copy = array(x.shape(), x.dtype(), nullptr, {});
-      copy_gpu(x, x_copy, CopyType::General, s);
+      array x_copy = contiguous_copy_gpu(x, s);
       out.copy_shared_buffer(x_copy);
       return x_copy;
     }
@@ -153,6 +152,7 @@ void Softmax::eval_gpu(const std::vector<array>& inputs, array& out) {
           kernel,
           n_rows,
           block_dim(),
+          0,
           in.data<DataType>(),
           out.data<DataType>(),
           axis_size);

mlx/backend/cuda/sort.cu

@@ -72,8 +72,7 @@ void gpu_sort(const Stream& s, array in, array& out_, int axis, bool argsort) {
   bool is_segmented_sort = in.flags().contiguous && in.strides()[axis] == 1;
   if (!is_segmented_sort) {
     array trans = swapaxes_in_eval(in, axis, last_dim);
-    in = array(trans.shape(), trans.dtype(), nullptr, {});
-    copy_gpu(trans, in, CopyType::General, s);
+    in = contiguous_copy_gpu(trans, s);
     encoder.add_temporary(in);
     out = array(allocator::malloc(out.nbytes()), in.shape(), out.dtype());
     encoder.add_temporary(out);

mlx/backend/cuda/ternary.cu

@@ -15,12 +15,27 @@ namespace cu {
 
 namespace cg = cooperative_groups;
 
-template <typename Op, typename T, typename IdxT>
+template <typename Op, typename T, typename IdxT, int N_READS>
 __global__ void
 ternary_v(const bool* a, const T* b, const T* c, T* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(a[index], b[index], c[index]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(a[i], b[i], c[i]);
+    }
+  } else {
+    auto a_vec = load_vector<N_READS>(a, index);
+    auto b_vec = load_vector<N_READS>(b, index);
+    auto c_vec = load_vector<N_READS>(c, index);
+
+    AlignedVector<T, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(a_vec.val[i], b_vec.val[i], c_vec.val[i]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
@@ -118,6 +133,7 @@ void ternary_op_gpu_inplace(
                     kernel,
                     num_blocks,
                     block_dims,
+                    0,
                     a.data<bool>(),
                     b.data<DType>(),
                     c.data<DType>(),
@@ -136,6 +152,7 @@ void ternary_op_gpu_inplace(
                   kernel,
                   num_blocks,
                   block_dims,
+                  0,
                   a.data<bool>(),
                   b.data<DType>(),
                   c.data<DType>(),
@@ -149,15 +166,23 @@ void ternary_op_gpu_inplace(
             }
           });
     } else {
-      dispatch_bool(out.data_size() > INT32_MAX, [&](auto large) {
+      dispatch_bool(out.data_size() > UINT32_MAX, [&](auto large) {
         using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
-        auto kernel = cu::ternary_v<Op, DType, IdxT>;
+        // TODO: Choose optimized value based on type size.
+        constexpr int N_READS = 4;
+        auto kernel = cu::ternary_v<Op, DType, IdxT, N_READS>;
         auto [num_blocks, block_dims] = get_launch_args(
-            kernel, out.data_size(), out.shape(), out.strides(), large());
+            kernel,
+            out.data_size(),
+            out.shape(),
+            out.strides(),
+            large(),
+            N_READS);
         encoder.add_kernel_node(
             kernel,
             num_blocks,
             block_dims,
+            0,
             a.data<bool>(),
             b.data<DType>(),
             c.data<DType>(),

mlx/backend/cuda/unary.cu

@@ -2,7 +2,6 @@
 
 #include "mlx/backend/common/unary.h"
 #include "mlx/backend/cuda/device.h"
-#include "mlx/backend/cuda/device/cucomplex_math.cuh"
 #include "mlx/backend/cuda/device/unary_ops.cuh"
 #include "mlx/backend/cuda/iterators/general_iterator.cuh"
 #include "mlx/backend/cuda/kernel_utils.cuh"
@@ -18,11 +17,24 @@ namespace cu {
 
 namespace cg = cooperative_groups;
 
-template <typename Op, typename In, typename Out, typename IdxT>
+template <typename Op, typename In, typename Out, typename IdxT, int N_READS>
 __global__ void unary_v(const In* in, Out* out, IdxT size) {
   IdxT index = cg::this_grid().thread_rank();
-  if (index < size) {
-    out[index] = Op{}(in[index]);
+
+  if ((index + 1) * N_READS > size) {
+    for (IdxT i = index * N_READS; i < size; ++i) {
+      out[i] = Op{}(in[i]);
+    }
+  } else {
+    auto in_vec = load_vector<N_READS>(in, index);
+
+    AlignedVector<Out, N_READS> out_vec;
+#pragma unroll
+    for (int i = 0; i < N_READS; ++i) {
+      out_vec.val[i] = Op{}(in_vec.val[i]);
+    }
+
+    store_vector<N_READS>(out, index, out_vec);
   }
 }
 
@@ -58,10 +70,10 @@ constexpr bool supports_unary_op() {
         !std::is_same_v<In, bool>;
   }
   if (std::is_same_v<Op, Ceil> || std::is_same_v<Op, Floor>) {
-    return std::is_same_v<In, Out> && !std::is_same_v<In, complex64_t>;
+    return std::is_same_v<In, Out> && !mlx::core::is_complex_v<In>;
   }
   if (std::is_same_v<Op, Conjugate>) {
-    return std::is_same_v<In, Out> && std::is_same_v<In, complex64_t>;
+    return std::is_same_v<In, Out> && mlx::core::is_complex_v<In>;
   }
   if (std::is_same_v<Op, ArcCos> || std::is_same_v<Op, ArcSin> ||
       std::is_same_v<Op, ArcTan> || std::is_same_v<Op, Cos> ||
@@ -75,7 +87,7 @@ constexpr bool supports_unary_op() {
     return std::is_same_v<In, Out> && is_inexact_v<In>;
   }
   if (std::is_same_v<Op, Imag> || std::is_same_v<Op, Real>) {
-    return std::is_same_v<In, complex64_t> && std::is_same_v<Out, float>;
+    return mlx::core::is_complex_v<In> && std::is_same_v<Out, float>;
   }
   if (std::is_same_v<Op, LogicalNot>) {
     return std::is_same_v<In, Out> && std::is_same_v<In, bool>;
@@ -89,7 +101,7 @@ template <typename Op>
 void unary_op_gpu_inplace(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   auto& in = inputs[0];
   if (in.size() == 0) {
@@ -112,22 +124,30 @@ void unary_op_gpu_inplace(
       using CTYPE_OUT = MLX_GET_TYPE(out_type_tag);
       if constexpr (cu::supports_unary_op<Op, CTYPE_IN, CTYPE_OUT>()) {
         dispatch_bool(large, [&](auto large) {
-          using IdxT = std::conditional_t<large(), int64_t, int32_t>;
           using InType = cuda_type_t<CTYPE_IN>;
           using OutType = cuda_type_t<CTYPE_OUT>;
-          using IdxT = std::conditional_t<large(), int64_t, int32_t>;
           if (contig) {
-            auto kernel = cu::unary_v<Op, InType, OutType, IdxT>;
+            using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
+            // TODO: Choose optimized value based on type size.
+            constexpr int N_READS = 4;
+            auto kernel = cu::unary_v<Op, InType, OutType, IdxT, N_READS>;
             auto [num_blocks, block_dims] = get_launch_args(
-                kernel, out.data_size(), out.shape(), out.strides(), large);
+                kernel,
+                out.data_size(),
+                out.shape(),
+                out.strides(),
+                large,
+                N_READS);
             encoder.add_kernel_node(
                 kernel,
                 num_blocks,
                 block_dims,
+                0,
                 in.data<InType>(),
                 out.data<OutType>(),
                 out.data_size());
           } else {
+            using IdxT = std::conditional_t<large(), int64_t, int32_t>;
             auto [shape, strides] = collapse_contiguous_dims(in);
             auto kernel = cu::unary_g<Op, InType, OutType, IdxT>;
             auto [num_blocks, block_dims] = get_launch_args(kernel, out, large);
@@ -135,6 +155,7 @@ void unary_op_gpu_inplace(
                 kernel,
                 num_blocks,
                 block_dims,
+                0,
                 in.data<InType>(),
                 out.data<OutType>(),
                 out.data_size(),
@@ -158,7 +179,7 @@ template <typename Op>
 void unary_op_gpu(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   set_unary_output_data(inputs[0], out);
   unary_op_gpu_inplace<Op>(inputs, out, op, s);
@@ -168,7 +189,7 @@ void unary_op_gpu(
   void func::eval_gpu(const std::vector<array>& inputs, array& out) { \
     nvtx3::scoped_range r(#func "::eval_gpu");                        \
     auto& s = out.primitive().stream();                               \
-    unary_op_gpu<cu::func>(inputs, out, get_primitive_string(this), s); \
+    unary_op_gpu<cu::func>(inputs, out, name(), s);                   \
   }
 
 UNARY_GPU(Abs)
@@ -204,16 +225,15 @@ UNARY_GPU(Tanh)
 void Log::eval_gpu(const std::vector<array>& inputs, array& out) {
   nvtx3::scoped_range r("Log::eval_gpu");
   auto& s = out.primitive().stream();
-  auto op = get_primitive_string(this);
   switch (base_) {
     case Base::e:
-      unary_op_gpu<cu::Log>(inputs, out, op, s);
+      unary_op_gpu<cu::Log>(inputs, out, name(), s);
       break;
     case Base::two:
-      unary_op_gpu<cu::Log2>(inputs, out, op, s);
+      unary_op_gpu<cu::Log2>(inputs, out, name(), s);
       break;
     case Base::ten:
-      unary_op_gpu<cu::Log10>(inputs, out, op, s);
+      unary_op_gpu<cu::Log10>(inputs, out, name(), s);
       break;
   }
 }
@@ -224,7 +244,7 @@ void Round::eval_gpu(const std::vector<array>& inputs, array& out) {
   const auto& in = inputs[0];
   auto& s = out.primitive().stream();
   if (issubdtype(in.dtype(), inexact)) {
-    unary_op_gpu<cu::Round>(inputs, out, get_primitive_string(this), s);
+    unary_op_gpu<cu::Round>(inputs, out, name(), s);
   } else {
     // No-op integer types
     out.copy_shared_buffer(in);

mlx/backend/cuda/utils.cpp

@@ -61,7 +61,7 @@ const char* dtype_to_cuda_type(const Dtype& dtype) {
     case float64:
       return "double";
     case complex64:
-      return "cuComplex";
+      return "complex64_t";
     default:
       return "unknown";
   }

mlx/backend/gpu/copy.cpp

@@ -46,4 +46,10 @@ void copy_gpu_inplace(
       in, out, in.shape(), i_strides, out.strides(), i_offset, 0, ctype, s);
 }
 
+array contiguous_copy_gpu(const array& arr, const Stream& s) {
+  array arr_copy(arr.shape(), arr.dtype(), nullptr, {});
+  copy_gpu(arr, arr_copy, CopyType::General, s);
+  return arr_copy;
+}
+
 } // namespace mlx::core

mlx/backend/gpu/copy.h

@@ -43,4 +43,7 @@ void copy_gpu_inplace(
 // Fill the output with the scalar val
 void fill_gpu(const array& val, array& out, const Stream& s);
 
+// Return a contiguous array with same shape that copies the data of |arr|.
+array contiguous_copy_gpu(const array& arr, const Stream& s);
+
 } // namespace mlx::core

mlx/backend/metal/CMakeLists.txt

@@ -63,6 +63,7 @@ if(MLX_METAL_JIT)
   make_jit_source(steel/gemm/kernels/steel_gemm_masked kernels/steel/defines.h)
   make_jit_source(steel/gemm/kernels/steel_gemm_gather)
   make_jit_source(steel/gemm/kernels/steel_gemm_splitk)
+  make_jit_source(steel/gemm/kernels/steel_gemm_segmented)
   make_jit_source(
     steel/conv/conv
     kernels/steel/utils.h

mlx/backend/metal/binary.cpp

@@ -7,20 +7,20 @@
 
 #define BINARY_GPU(func)                                              \
   void func::eval_gpu(const std::vector<array>& inputs, array& out) { \
-    binary_op_gpu(inputs, out, get_primitive_string(this));           \
+    binary_op_gpu(inputs, out, name());                               \
   }
 
 #define BINARY_GPU_MULTI(func)                                         \
   void func::eval_gpu(                                                 \
       const std::vector<array>& inputs, std::vector<array>& outputs) { \
-    binary_op_gpu(inputs, outputs, get_primitive_string(this));        \
+    binary_op_gpu(inputs, outputs, name());                            \
   }
 
 namespace mlx::core {
 
 std::string get_kernel_name(
     BinaryOpType bopt,
-    const std::string& op,
+    const char* op,
     const array& a,
     bool large,
     int ndim,
@@ -65,7 +65,7 @@ std::string get_kernel_name(
 void binary_op_gpu_inplace(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   auto& a = inputs[0];
   auto& b = inputs[1];
@@ -165,7 +165,7 @@ void binary_op_gpu_inplace(
 void binary_op_gpu(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   assert(inputs.size() == 2);
   auto& a = inputs[0];
@@ -179,7 +179,7 @@ void binary_op_gpu(
 void binary_op_gpu(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    const std::string& op) {
+    const char* op) {
   auto& s = outputs[0].primitive().stream();
   binary_op_gpu(inputs, outputs, op, s);
 }
@@ -187,7 +187,7 @@ void binary_op_gpu(
 void binary_op_gpu_inplace(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   std::vector<array> outputs = {out};
   binary_op_gpu_inplace(inputs, outputs, op, s);
@@ -196,7 +196,7 @@ void binary_op_gpu_inplace(
 void binary_op_gpu(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s) {
   assert(inputs.size() == 2);
   auto& a = inputs[0];
@@ -209,7 +209,7 @@ void binary_op_gpu(
 void binary_op_gpu(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op) {
+    const char* op) {
   auto& s = out.primitive().stream();
   binary_op_gpu(inputs, out, op, s);
 }
@@ -237,19 +237,19 @@ BINARY_GPU(Subtract)
 void BitwiseBinary::eval_gpu(const std::vector<array>& inputs, array& out) {
   switch (op_) {
     case BitwiseBinary::And:
-      binary_op_gpu(inputs, out, get_primitive_string(this));
+      binary_op_gpu(inputs, out, name());
       break;
     case BitwiseBinary::Or:
-      binary_op_gpu(inputs, out, get_primitive_string(this));
+      binary_op_gpu(inputs, out, name());
       break;
     case BitwiseBinary::Xor:
-      binary_op_gpu(inputs, out, get_primitive_string(this));
+      binary_op_gpu(inputs, out, name());
       break;
     case BitwiseBinary::LeftShift:
-      binary_op_gpu(inputs, out, get_primitive_string(this));
+      binary_op_gpu(inputs, out, name());
       break;
     case BitwiseBinary::RightShift:
-      binary_op_gpu(inputs, out, get_primitive_string(this));
+      binary_op_gpu(inputs, out, name());
       break;
   }
 }

mlx/backend/metal/binary.h

@@ -9,25 +9,25 @@ namespace mlx::core {
 void binary_op_gpu(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    const std::string& op,
+    const char* op,
     const Stream& s);
 
 void binary_op_gpu(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s);
 
 void binary_op_gpu_inplace(
     const std::vector<array>& inputs,
     std::vector<array>& outputs,
-    const std::string& op,
+    const char* op,
     const Stream& s);
 
 void binary_op_gpu_inplace(
     const std::vector<array>& inputs,
     array& out,
-    const std::string& op,
+    const char* op,
     const Stream& s);
 
 } // namespace mlx::core

mlx/backend/metal/compiled.cpp

@@ -212,9 +212,7 @@ inline void build_kernel(
           get_type_string(x.dtype()),
           namer.get_name(x.inputs()[0]));
     } else {
-      std::ostringstream ss;
-      x.primitive().print(ss);
-      os += ss.str();
+      os += x.primitive().name();
       os += "()(";
       for (int i = 0; i < x.inputs().size() - 1; i++) {
         os += fmt::format("tmp_{0}, ", namer.get_name(x.inputs()[i]));

mlx/backend/metal/conv.cpp

@@ -149,8 +149,7 @@ void explicit_gemm_conv_group_ND_gpu(
       wt, {wt.strides(0), 1, C_per_group}, wt.flags(), wt.size());
 
   // Materialize
-  auto wt_transpose = array(wt_view.shape(), wt_view.dtype(), nullptr, {});
-  copy_gpu(wt_view, wt_transpose, CopyType::General, s);
+  array wt_transpose = contiguous_copy_gpu(wt_view, s);
 
   // Perform gemm
   std::vector<array> copies = {in_unfolded, wt_transpose};
@@ -961,16 +960,12 @@ void Convolution::eval_gpu(const std::vector<array>& inputs, array& out) {
   auto in = inputs[0];
   auto wt = inputs[1];
   if (!in.flags().row_contiguous) {
-    array arr_copy(in.shape(), in.dtype(), nullptr, {});
-    copy_gpu(in, arr_copy, CopyType::General, s);
-    copies.push_back(arr_copy);
-    in = arr_copy;
+    in = contiguous_copy_gpu(in, s);
+    copies.push_back(in);
   }
   if (!wt.flags().row_contiguous) {
-    array arr_copy(wt.shape(), wt.dtype(), nullptr, {});
-    copy_gpu(wt, arr_copy, CopyType::General, s);
-    copies.push_back(arr_copy);
-    wt = arr_copy;
+    wt = contiguous_copy_gpu(wt, s);
+    copies.push_back(wt);
   }
 
   // 3D conv

mlx/backend/metal/copy.cpp

@@ -86,7 +86,7 @@ void copy_gpu_inplace(
     }
   } else {
     work_per_thread = get_work_per_thread(out.dtype(), out.data_size());
-    if (work_per_thread > 1) {
+    if (!large && work_per_thread > 1) {
       kernel_name += "n";
     }
   }

mlx/backend/metal/device.cpp

@@ -1,20 +1,18 @@
 // Copyright © 2023-2024 Apple Inc.
 
 #include <cstdlib>
-#include <filesystem>
 #include <sstream>
 
 #define NS_PRIVATE_IMPLEMENTATION
 #define CA_PRIVATE_IMPLEMENTATION
 #define MTL_PRIVATE_IMPLEMENTATION
 
+#include "mlx/backend/common/utils.h"
 #include "mlx/backend/metal/device.h"
 #include "mlx/backend/metal/metal.h"
 #include "mlx/backend/metal/utils.h"
 #include "mlx/utils.h"
 
-namespace fs = std::filesystem;
-
 namespace mlx::core::metal {
 
 namespace {
@@ -80,12 +78,7 @@ MTL::Library* try_load_bundle(
 std::pair<MTL::Library*, NS::Error*> load_colocated_library(
     MTL::Device* device,
     const std::string& relative_path) {
-  std::string binary_dir = get_binary_directory();
-  if (binary_dir.size() == 0) {
-    return {nullptr, nullptr};
-  }
-
-  auto path = fs::path(binary_dir) / relative_path;
+  auto path = current_binary_dir() / relative_path;
   if (!path.has_extension()) {
     path.replace_extension(".metallib");
   }
@@ -197,7 +190,7 @@ MTL::Library* load_library(
 
   std::ostringstream msg;
   msg << "Failed to load the metallib " << lib_name << ".metallib. "
-      << "We attempted to load it from <" << get_binary_directory() << "/"
+      << "We attempted to load it from <" << current_binary_dir() << "/"
       << lib_name << ".metallib" << ">";
 #ifdef SWIFTPM_BUNDLE
   msg << " and from the Swift PM bundle.";

mlx/backend/metal/device.h

@@ -3,8 +3,6 @@
 #pragma once
 
 #include <Metal/Metal.hpp>
-#include <dlfcn.h>
-#include <filesystem>
 #include <functional>
 #include <mutex>
 #include <shared_mutex>
@@ -15,22 +13,8 @@
 #include "mlx/array.h"
 #include "mlx/device.h"
 
-namespace fs = std::filesystem;
-
 namespace mlx::core::metal {
 
-// Note, this function must be left inline in a header so that it is not
-// dynamically linked.
-inline std::string get_binary_directory() {
-  Dl_info info;
-  std::string directory;
-  int success = dladdr((void*)get_binary_directory, &info);
-  if (success) {
-    directory = fs::path(info.dli_fname).remove_filename().c_str();
-  }
-  return directory;
-}
-
 using MTLFCList =
     std::vector<std::tuple<const void*, MTL::DataType, NS::UInteger>>;
 

mlx/backend/metal/indexing.cpp

@@ -575,9 +575,17 @@ void ScatterAxis::eval_gpu(const std::vector<array>& inputs, array& out) {
   compute_encoder.set_output_array(out, 2);
 
   // Set source info
+  if (ndim > 1) {
     compute_encoder.set_vector_bytes(remove_index(idx.shape(), axis_), 3);
     compute_encoder.set_vector_bytes(remove_index(upd.strides(), axis_), 4);
     compute_encoder.set_vector_bytes(remove_index(idx.strides(), axis_), 5);
+  } else {
+    // The following will be ignored in the kernel but we still have to set
+    // some value so that metal validation passes.
+    compute_encoder.set_vector_bytes(idx.shape(), 3);
+    compute_encoder.set_vector_bytes(upd.strides(), 4);
+    compute_encoder.set_vector_bytes(idx.strides(), 5);
+  }
   compute_encoder.set_bytes(ndim - 1, 6);
   compute_encoder.set_bytes(axis_, 7);
   compute_encoder.set_bytes(out.shape(axis_), 8);

mlx/backend/metal/jit/includes.h

@@ -34,6 +34,7 @@ const char* steel_gemm_fused();
 const char* steel_gemm_masked();
 const char* steel_gemm_splitk();
 const char* steel_gemm_gather();
+const char* steel_gemm_segmented();
 const char* conv();
 const char* steel_conv();
 const char* steel_conv_general();

mlx/backend/metal/jit_kernels.cpp

@@ -8,12 +8,6 @@ using namespace fmt::literals;
 
 namespace mlx::core {
 
-std::string op_name(const array& arr) {
-  std::ostringstream op_t;
-  arr.primitive().print(op_t);
-  return op_t.str();
-}
-
 MTL::ComputePipelineState* get_arange_kernel(
     metal::Device& d,
     const std::string& kernel_name,
@@ -33,7 +27,7 @@ MTL::ComputePipelineState* get_unary_kernel(
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op) {
+    const char* op) {
   std::string lib_name = kernel_name.substr(kernel_name.find("_") + 1);
   auto lib = d.get_library(lib_name, [&]() {
     auto in_t = get_type_string(in_type);
@@ -58,10 +52,10 @@ MTL::ComputePipelineState* get_unary_kernel(
 }
 
 void append_binary_kernels(
-    const std::string lib_name,
+    const std::string& lib_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op,
+    const char* op,
     std::string& kernel_source) {
   const std::array<std::pair<std::string, std::string>, 7> kernel_types = {{
       {"ss", "binary_ss"},
@@ -112,7 +106,7 @@ MTL::ComputePipelineState* get_binary_kernel(
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op) {
+    const char* op) {
   std::string lib_name = kernel_name.substr(kernel_name.find("_") + 1);
   auto lib = d.get_library(lib_name, [&]() {
     std::string kernel_source;
@@ -129,7 +123,7 @@ MTL::ComputePipelineState* get_binary_two_kernel(
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op) {
+    const char* op) {
   std::string lib_name = kernel_name.substr(kernel_name.find("_") + 1);
   auto lib = d.get_library(lib_name, [&]() {
     std::string kernel_source = metal::utils();
@@ -144,7 +138,7 @@ MTL::ComputePipelineState* get_ternary_kernel(
     metal::Device& d,
     const std::string& kernel_name,
     Dtype type,
-    const std::string op) {
+    const char* op) {
   std::string lib_name = kernel_name.substr(kernel_name.find("_") + 1);
   auto lib = d.get_library(lib_name, [&]() {
     auto t_str = get_type_string(type);
@@ -652,6 +646,43 @@ MTL::ComputePipelineState* get_steel_gemm_gather_kernel(
   return d.get_kernel(kernel_name, lib, hash_name, func_consts);
 }
 
+MTL::ComputePipelineState* get_steel_gemm_segmented_kernel(
+    metal::Device& d,
+    const std::string& kernel_name,
+    const std::string& hash_name,
+    const metal::MTLFCList& func_consts,
+    const array& out,
+    bool transpose_a,
+    bool transpose_b,
+    int bm,
+    int bn,
+    int bk,
+    int wm,
+    int wn) {
+  const auto& lib_name = kernel_name;
+  auto lib = d.get_library(lib_name, [&]() {
+    std::string kernel_source;
+    concatenate(
+        kernel_source,
+        metal::utils(),
+        metal::gemm(),
+        metal::steel_gemm_segmented(),
+        get_template_definition(
+            lib_name,
+            "segmented_mm",
+            get_type_string(out.dtype()),
+            bm,
+            bn,
+            bk,
+            wm,
+            wn,
+            transpose_a,
+            transpose_b));
+    return kernel_source;
+  });
+  return d.get_kernel(kernel_name, lib, hash_name, func_consts);
+}
+
 MTL::ComputePipelineState* get_gemv_masked_kernel(
     metal::Device& d,
     const std::string& kernel_name,

mlx/backend/metal/kernels.h

@@ -19,27 +19,27 @@ MTL::ComputePipelineState* get_unary_kernel(
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op);
+    const char* op);
 
 MTL::ComputePipelineState* get_binary_kernel(
     metal::Device& d,
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op);
+    const char* op);
 
 MTL::ComputePipelineState* get_binary_two_kernel(
     metal::Device& d,
     const std::string& kernel_name,
     Dtype in_type,
     Dtype out_type,
-    const std::string op);
+    const char* op);
 
 MTL::ComputePipelineState* get_ternary_kernel(
     metal::Device& d,
     const std::string& kernel_name,
     Dtype type,
-    const std::string op);
+    const char* op);
 
 MTL::ComputePipelineState* get_copy_kernel(
     metal::Device& d,
@@ -175,6 +175,20 @@ MTL::ComputePipelineState* get_steel_gemm_gather_kernel(
     int wn,
     bool rhs);
 
+MTL::ComputePipelineState* get_steel_gemm_segmented_kernel(
+    metal::Device& d,
+    const std::string& kernel_name,
+    const std::string& hash_name,
+    const metal::MTLFCList& func_consts,
+    const array& out,
+    bool transpose_a,
+    bool transpose_b,
+    int bm,
+    int bn,
+    int bk,
+    int wm,
+    int wn);
+
 MTL::ComputePipelineState* get_steel_conv_kernel(
     metal::Device& d,
     const std::string& kernel_name,
@@ -243,8 +257,10 @@ MTL::ComputePipelineState* get_gather_qmm_kernel(
 
 // Create a GPU kernel template definition for JIT compilation
 template <typename... Args>
-std::string
-get_template_definition(std::string name, std::string func, Args... args) {
+std::string get_template_definition(
+    std::string_view name,
+    std::string_view func,
+    Args... args) {
   std::ostringstream s;
   s << func << "<";
   bool first = true;