Refactoring launcher

.github/actions/build-cuda-release/action.yml

@@ -1,15 +1,6 @@
 name: 'Build CUDA wheel'
 description: 'Build CUDA wheel'
 
-inputs:
-  arch:
-    description: 'Platform architecture tag'
-    required: true
-    type: choice
-    options:
-      - x86_64
-      - aarch64
-
 runs:
   using: "composite"
   steps:
@@ -21,4 +12,4 @@ runs:
         pip install auditwheel build patchelf setuptools
         python setup.py clean --all
         MLX_BUILD_STAGE=2 python -m build -w
-        bash python/scripts/repair_cuda.sh ${{ inputs.arch }}
+        bash python/scripts/repair_cuda.sh

.github/actions/setup-linux/action.yml

@@ -15,7 +15,6 @@ runs:
   using: "composite"
   steps:
     - name: Use ccache
-      if: ${{ runner.arch == 'x86_64' }}
       uses: hendrikmuhs/ccache-action@v1.2
       with:
         key: ccache-${{ runner.os }}-${{ runner.arch }}-${{ inputs.toolkit }}-py${{ inputs.python-version }}

.github/workflows/release.yml

@@ -128,11 +128,7 @@ jobs:
 
   build_cuda_release:
     if: github.repository == 'ml-explore/mlx'
-    strategy:
-      matrix:
-        arch: ['x86_64', 'aarch64']
-        toolkit: ['cuda-12.9', 'cuda-13.0']
-    runs-on: ${{ matrix.arch == 'x86_64' && 'ubuntu-22-large' || 'ubuntu-22-large-arm' }}
+    runs-on: ubuntu-22-large
     env:
       PYPI_RELEASE: 1
       DEV_RELEASE: ${{ github.event.inputs.dev_release == 'true' && 1 || 0 }}
@@ -140,11 +136,9 @@ jobs:
       - uses: actions/checkout@v6
       - uses: ./.github/actions/setup-linux
         with:
-          toolkit: ${{ matrix.toolkit }}
+          toolkit: 'cuda-12.9'
       - name: Build Python package
         uses: ./.github/actions/build-cuda-release
-        with:
-          arch: ${{ matrix.arch }}
       - name: Upload artifacts
         uses: actions/upload-artifact@v5
         with:

docs/src/install.rst

@@ -29,20 +29,17 @@ MLX has a CUDA backend which you can install with:
 
 .. code-block:: shell
 
-    pip install mlx[cuda12]
-
+    pip install mlx[cuda]
 
 To install the CUDA package from PyPi your system must meet the following
 requirements:
 
-- Nvidia architecture >= SM 7.5
+- Nvidia architecture >= SM 7.0 (Volta)
 - Nvidia driver >= 550.54.14
 - CUDA toolkit >= 12.0
 - Linux distribution with glibc >= 2.35
 - Python >= 3.10
 
-For CUDA 13 use ``pip install mlx[cuda13]``. The CUDA 13 package requires
-an Nvidia driver >= 580 or an appropriate CUDA compatibility package.
 
 CPU-only (Linux)
 ^^^^^^^^^^^^^^^^

mlx/CMakeLists.txt

@@ -1,6 +1,7 @@
 target_sources(
   mlx
-  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/array.cpp
+  PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/allocator.cpp
+          ${CMAKE_CURRENT_SOURCE_DIR}/array.cpp
           ${CMAKE_CURRENT_SOURCE_DIR}/compile.cpp
           ${CMAKE_CURRENT_SOURCE_DIR}/device.cpp
           ${CMAKE_CURRENT_SOURCE_DIR}/dtype.cpp

mlx/allocator.cpp

@@ -0,0 +1,24 @@
+// Copyright © 2023 Apple Inc.
+
+#include <cstdlib>
+#include <sstream>
+
+#include "mlx/allocator.h"
+
+namespace mlx::core::allocator {
+
+Buffer malloc(size_t size) {
+  auto buffer = allocator().malloc(size);
+  if (size && !buffer.ptr()) {
+    std::ostringstream msg;
+    msg << "[malloc] Unable to allocate " << size << " bytes.";
+    throw std::runtime_error(msg.str());
+  }
+  return buffer;
+}
+
+void free(Buffer buffer) {
+  allocator().free(buffer);
+}
+
+} // namespace mlx::core::allocator

mlx/allocator.h

@@ -28,16 +28,16 @@ class Buffer {
   };
 };
 
+Buffer malloc(size_t size);
+
+void free(Buffer buffer);
+
 class Allocator {
   /** Abstract base class for a memory allocator. */
  public:
   virtual Buffer malloc(size_t size) = 0;
   virtual void free(Buffer buffer) = 0;
   virtual size_t size(Buffer buffer) const = 0;
-  virtual Buffer make_buffer(void* ptr, size_t size) {
-    return Buffer{nullptr};
-  };
-  virtual void release(Buffer buffer) {}
 
   Allocator() = default;
   Allocator(const Allocator& other) = delete;
@@ -49,25 +49,4 @@ class Allocator {
 
 Allocator& allocator();
 
-inline Buffer malloc(size_t size) {
-  return allocator().malloc(size);
-}
-
-inline void free(Buffer buffer) {
-  allocator().free(buffer);
-}
-
-// Make a Buffer from a raw pointer of the given size without a copy.  If a
-// no-copy conversion is not possible then the returned buffer.ptr() will be
-// nullptr. Any buffer created with this function must be released with
-// release(buffer)
-inline Buffer make_buffer(void* ptr, size_t size) {
-  return allocator().make_buffer(ptr, size);
-};
-
-// Release a buffer from the allocator made with make_buffer
-inline void release(Buffer buffer) {
-  allocator().release(buffer);
-}
-
 } // namespace mlx::core::allocator

mlx/array.cpp

@@ -82,28 +82,6 @@ array::array(std::initializer_list<int> data, Dtype dtype)
   init(data.begin());
 }
 
-array::array(
-    void* data,
-    Shape shape,
-    Dtype dtype,
-    const std::function<void(void*)>& deleter)
-    : array_desc_(std::make_shared<ArrayDesc>(std::move(shape), dtype)) {
-  auto buffer = allocator::make_buffer(data, nbytes());
-  if (buffer.ptr() == nullptr) {
-    set_data(allocator::malloc(nbytes()));
-    auto ptr = static_cast<char*>(data);
-    std::copy(ptr, ptr + nbytes(), this->data<char>());
-    deleter(data);
-  } else {
-    auto wrapped_deleter = [deleter](allocator::Buffer buffer) {
-      auto ptr = buffer.ptr();
-      allocator::release(buffer);
-      return deleter(ptr);
-    };
-    set_data(buffer, std::move(wrapped_deleter));
-  }
-}
-
 /* Build an array from a shared buffer */
 array::array(allocator::Buffer data, Shape shape, Dtype dtype, Deleter deleter)
     : array_desc_(std::make_shared<ArrayDesc>(std::move(shape), dtype)) {

mlx/array.h

@@ -57,16 +57,6 @@ class array {
       Shape shape,
       Dtype dtype = TypeToDtype<T>());
 
-  /* Build an array from a raw pointer. The constructor will attempt to use the
-   * input data without a copy. The deleter will be called when the array no
-   * longer needs the underlying memory - after the array is destroyed in the
-   * no-copy case and after the copy otherwise. */
-  explicit array(
-      void* data,
-      Shape shape,
-      Dtype dtype,
-      const std::function<void(void*)>& deleter);
-
   /* Build an array from a buffer */
   explicit array(
       allocator::Buffer data,

mlx/backend/cuda/allocator.cpp

@@ -20,19 +20,6 @@ constexpr int page_size = 16384;
 // Any allocations smaller than this will try to use the small pool
 constexpr int small_block_size = 8;
 
-#if CUDART_VERSION >= 13000
-inline cudaMemLocation cuda_mem_loc(int i) {
-  cudaMemLocation loc;
-  loc.type = cudaMemLocationTypeDevice;
-  loc.id = i;
-  return loc;
-}
-#else
-inline int cuda_mem_loc(int i) {
-  return i;
-}
-#endif // CUDART_VERSION >= 13000
-
 // 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;
@@ -48,7 +35,13 @@ SmallSizePool::SmallSizePool() {
   int device_count = 0;
   CHECK_CUDA_ERROR(cudaGetDeviceCount(&device_count));
   for (int i = 0; i < device_count; ++i) {
-    auto loc = cuda_mem_loc(i);
+#if CUDART_VERSION >= 13000
+    cudaMemLocation loc;
+    loc.type = cudaMemLocationTypeDevice;
+    loc.id = i;
+#else
+    int loc = i;
+#endif // CUDART_VERSION >= 13000
     CHECK_CUDA_ERROR(
         cudaMemAdvise(data_, small_pool_size, cudaMemAdviseSetAccessedBy, loc));
   }
@@ -97,10 +90,9 @@ CudaAllocator::CudaAllocator()
           page_size,
           [](CudaBuffer* buf) { return buf->size; },
           [this](CudaBuffer* buf) { cuda_free(buf); }) {
-  size_t free;
-  CHECK_CUDA_ERROR(cudaMemGetInfo(&free, &total_memory_));
-  memory_limit_ = total_memory_ * 0.95;
-  free_limit_ = total_memory_ - memory_limit_;
+  size_t free, total;
+  CHECK_CUDA_ERROR(cudaMemGetInfo(&free, &total));
+  memory_limit_ = total * 0.9;
   max_pool_size_ = memory_limit_;
 
   int device_count = 0;
@@ -112,10 +104,6 @@ CudaAllocator::CudaAllocator()
     cudaStream_t s;
     CHECK_CUDA_ERROR(cudaStreamCreateWithFlags(&s, cudaStreamNonBlocking));
     free_streams_.push_back(s);
-
-    cudaMemPool_t mem_pool;
-    CHECK_CUDA_ERROR(cudaDeviceGetDefaultMemPool(&mem_pool, i));
-    mem_pools_.push_back(mem_pool);
   }
   CHECK_CUDA_ERROR(cudaSetDevice(curr));
 }
@@ -166,35 +154,23 @@ CudaAllocator::malloc_async(size_t size, int device, cudaStream_t stream) {
     }
     lock.unlock();
     if (!buf) {
+      cudaError_t err;
       void* data = nullptr;
       if (device == -1) {
-        CHECK_CUDA_ERROR(cudaMallocManaged(&data, size));
+        err = cudaMallocManaged(&data, size);
       } else {
-        CHECK_CUDA_ERROR(cudaMallocAsync(&data, size, stream));
+        err = cudaMallocAsync(&data, size, stream);
+      }
+      if (err != cudaSuccess && err != cudaErrorMemoryAllocation) {
+        throw std::runtime_error(fmt::format(
+            "cudaMallocManaged failed: {}.", cudaGetErrorString(err)));
       }
       if (!data) {
-        std::ostringstream msg;
-        msg << "[malloc] Unable to allocate " << size << " bytes.";
-        throw std::runtime_error(msg.str());
+        return Buffer{nullptr};
       }
       buf = new CudaBuffer{data, size, device};
     }
     lock.lock();
-
-    // If any cuda memory pool has too much reserved memory, clear some
-    // memory from the cache. This prevents graph / kernel execution failing
-    // from OOM
-    if (get_cache_memory() > 0) {
-      for (auto p : mem_pools_) {
-        size_t used = 0;
-        CHECK_CUDA_ERROR(cudaMemPoolGetAttribute(
-            p, cudaMemPoolAttrReservedMemCurrent, &used));
-        if (used > (total_memory_ - free_limit_)) {
-          buffer_cache_.release_cached_buffers(free_limit_);
-          break;
-        }
-      }
-    }
   }
   active_memory_ += buf->size;
   peak_memory_ = std::max(active_memory_, peak_memory_);

mlx/backend/cuda/allocator.h

@@ -71,14 +71,11 @@ class CudaAllocator : public allocator::Allocator {
 
   std::mutex mutex_;
   size_t memory_limit_;
-  size_t free_limit_;
-  size_t total_memory_;
   size_t max_pool_size_;
   BufferCache<CudaBuffer> buffer_cache_;
   size_t active_memory_{0};
   size_t peak_memory_{0};
   std::vector<cudaStream_t> free_streams_;
-  std::vector<cudaMemPool_t> mem_pools_;
   SmallSizePool scalar_pool_;
 };
 

mlx/backend/cuda/copy/copy_general_input.cu

@@ -95,14 +95,11 @@ void copy_general_input(
             const InType* in_ptr = gpu_ptr<InType>(in) + offset_in;
             OutType* out_ptr = gpu_ptr<OutType>(out) + offset_out;
             int ndim = shape.size();
-
-            int work_per_thread = 8;
+            int work_per_thread = 1;
             auto dim0 = ndim > 0 ? shape.back() : 1;
             auto rest = out.size() / dim0;
-            if (dim0 >= 4 && dim0 < 8) {
+            if (dim0 >= 4) {
               work_per_thread = 4;
-            } else if (dim0 < 4) {
-              work_per_thread = 1;
             }
             dim0 = (dim0 + work_per_thread - 1) / work_per_thread;
             auto block_dims = get_block_dims(dim0, rest, 1);
@@ -113,10 +110,7 @@ void copy_general_input(
               dispatch_1_2_3(ndim, [&](auto dims_constant) {
                 auto kernel =
                     cu::copy_g_nd<InType, OutType, IdxT, dims_constant(), 1>;
-                if (work_per_thread == 8) {
-                  kernel =
-                      cu::copy_g_nd<InType, OutType, IdxT, dims_constant(), 8>;
-                } else if (work_per_thread == 4) {
+                if (work_per_thread == 4) {
                   kernel =
                       cu::copy_g_nd<InType, OutType, IdxT, dims_constant(), 4>;
                 }
@@ -133,9 +127,7 @@ void copy_general_input(
               });
             } else { // ndim >= 4
               auto kernel = cu::copy_g<InType, OutType, IdxT, 1>;
-              if (work_per_thread == 8) {
-                kernel = cu::copy_g<InType, OutType, IdxT, 8>;
-              } else if (work_per_thread == 4) {
+              if (work_per_thread == 4) {
                 kernel = cu::copy_g<InType, OutType, IdxT, 4>;
               }
               encoder.add_kernel_node(

mlx/backend/cuda/device.cpp

@@ -318,52 +318,46 @@ void CommandEncoder::add_kernel_node(const CUDA_KERNEL_NODE_PARAMS& params) {
   insert_graph_dependencies(GraphNode{node, "K"});
 }
 
-std::pair<std::string, bool> subgraph_to_key(cudaGraph_t graph) {
-  // Constructs a key representing the nodes of a sub-graph.
-  // Also checks if the sub-graph is updatable as CUDA graphs do not get
-  // updated correctly if a kernel node getting updated has a different cluster
-  // shape than the node it's being updated with.
-  std::string key = "(";
+bool is_graph_updatable(cudaGraph_t graph, int& cluster_dim_x) {
+  // CUDA graphs do not get updated correctly if a kernel node getting updated
+  // has a different cluster shape than the node it's being updated with.
   size_t num_nodes = 0;
   CHECK_CUDA_ERROR(cudaGraphGetNodes(graph, nullptr, &num_nodes));
   if (num_nodes == 0) {
-    return {key + ")", true};
+    return true;
   }
-  bool is_updatable = true;
+
   std::vector<cudaGraphNode_t> nodes(num_nodes);
   CHECK_CUDA_ERROR(cudaGraphGetNodes(graph, nodes.data(), &num_nodes));
   for (const auto& node : nodes) {
-    if (!is_updatable) {
-      break;
-    }
     cudaGraphNodeType type;
     CHECK_CUDA_ERROR(cudaGraphNodeGetType(node, &type));
     if (type == cudaGraphNodeTypeGraph) {
       // Try to be updatable for a structure like graph -> graph -> kernel
+      if (num_nodes > 1) {
+        return false;
+      }
       cudaGraph_t child;
       CHECK_CUDA_ERROR(cudaGraphChildGraphNodeGetGraph(node, &child));
-      auto [subkey, sub_is_updatable] = subgraph_to_key(child);
-      is_updatable &= sub_is_updatable;
-      key += subkey;
-    } else if (type == cudaGraphNodeTypeMemset) {
-      key += "M";
+      return is_graph_updatable(child, cluster_dim_x);
     } else if (type != cudaGraphNodeTypeKernel) {
-      is_updatable = false;
+      return false;
     } else {
       cudaLaunchAttributeValue cluster_dim;
       CHECK_CUDA_ERROR(cudaGraphKernelNodeGetAttribute(
           node, cudaLaunchAttributeClusterDimension, &cluster_dim));
-      // Only allow dim.x to be greater than 1
+      // Only dim.x can be greater than 1
       if (cluster_dim.clusterDim.y > 1 || cluster_dim.clusterDim.z > 1) {
-        is_updatable = false;
-      } else {
-        key += "K";
-        key += std::to_string(cluster_dim.clusterDim.x);
+        return false;
       }
+      // Only one child node allowed when subgraph uses clusters
+      if (cluster_dim.clusterDim.x > 0 && num_nodes > 1) {
+        return false;
+      }
+      cluster_dim_x = cluster_dim.clusterDim.x;
     }
   }
-  key += ")";
-  return {key, is_updatable};
+  return true;
 }
 
 void CommandEncoder::add_graph_node(cudaGraph_t child) {
@@ -376,10 +370,11 @@ void CommandEncoder::add_graph_node(cudaGraph_t child) {
     return;
   }
   cudaGraphNode_t node;
-  auto [sub_graph_key, is_updatable] = subgraph_to_key(child);
-  is_graph_updatable_ &= is_updatable;
+  int cluster_dim_x = 0;
+  is_graph_updatable_ &= is_graph_updatable(child, cluster_dim_x);
   CHECK_CUDA_ERROR(cudaGraphAddChildGraphNode(&node, graph_, NULL, 0, child));
-  insert_graph_dependencies(GraphNode{node, sub_graph_key});
+  insert_graph_dependencies(
+      GraphNode{node, "G" + std::to_string(cluster_dim_x)});
 }
 
 bool CommandEncoder::needs_commit() {

mlx/backend/cuda/device.h

@@ -106,7 +106,7 @@ class CommandEncoder {
     cudaGraphNode_t node;
     // K = kernel
     // E = empty
-    // () = subgraph (with metadata)
+    // G* = subgraph (with metadata)
     // Symbols ':', '-' are reserved as separators
     std::string node_type;
     std::string id;

mlx/backend/cuda/reduce/col_reduce.cu

@@ -89,13 +89,9 @@ template <
     int NDIM,
     int BM,
     int BN,
-    int N_READS = 4,
-    int BLOCKS = 1>
-__global__ void col_reduce_looped(
-    T* in,
-    U* out,
-    const __grid_constant__ ColReduceArgs args,
-    int64_t out_size) {
+    int N_READS = 4>
+__global__ void
+col_reduce_looped(T* in, U* out, const __grid_constant__ ColReduceArgs args) {
   auto grid = cg::this_grid();
   auto block = cg::this_thread_block();
   auto warp = cg::tiled_partition<WARP_SIZE>(block);
@@ -106,8 +102,6 @@ __global__ void col_reduce_looped(
   size_t tile_idx = grid.block_rank();
   size_t tile_x = tile_idx % ((args.reduction_stride + BN - 1) / BN);
   size_t tile_y = tile_idx / ((args.reduction_stride + BN - 1) / BN);
-  size_t tile_out = tile_y / out_size;
-  tile_y = tile_y % out_size;
 
   // Compute the indices for the thread within the tile
   short thread_x = block.thread_rank() % threads_per_row;
@@ -124,23 +118,12 @@ __global__ void col_reduce_looped(
     totals[i] = ReduceInit<Op, T>::value();
   }
 
-  size_t total = args.non_col_reductions * args.reduction_size;
-  size_t per_block, start, end;
-  if constexpr (BLOCKS > 1) {
-    per_block = (total + BLOCKS - 1) / BLOCKS;
-    start = tile_out * per_block + thread_y;
-    end = min((tile_out + 1) * per_block, total);
-  } else {
-    per_block = total;
-    start = thread_y;
-    end = total;
-  }
-
   LoopedElemToLoc<NDIM, (NDIM > 2)> loop(args.reduce_ndim);
-  loop.next(start, args.reduce_shape.data(), args.reduce_strides.data());
+  loop.next(thread_y, args.reduce_shape.data(), args.reduce_strides.data());
+  size_t total = args.non_col_reductions * args.reduction_size;
   if (tile_x * BN + BN <= args.reduction_stride) {
     if (args.reduction_stride % N_READS == 0) {
-      for (size_t r = start; r < end; r += BM) {
+      for (size_t r = thread_y; r < total; r += BM) {
         T vals[N_READS];
         cub::LoadDirectBlockedVectorized(thread_x, in + loop.location(), vals);
         for (int i = 0; i < N_READS; i++) {
@@ -149,7 +132,7 @@ __global__ void col_reduce_looped(
         loop.next(BM, args.reduce_shape.data(), args.reduce_strides.data());
       }
     } else {
-      for (size_t r = start; r < end; r += BM) {
+      for (size_t r = thread_y; r < total; r += BM) {
         T vals[N_READS];
         cub::LoadDirectBlocked(thread_x, in + loop.location(), vals);
         for (int i = 0; i < N_READS; i++) {
@@ -159,7 +142,7 @@ __global__ void col_reduce_looped(
       }
     }
   } else {
-    for (size_t r = start; r < end; r += BM) {
+    for (size_t r = thread_y; r < total; r += BM) {
       T vals[N_READS];
       cub::LoadDirectBlocked(
           thread_x,
@@ -190,9 +173,6 @@ __global__ void col_reduce_looped(
 
   // Write result.
   if (warp.thread_rank() == 0) {
-    if (BLOCKS > 1) {
-      out += tile_out * out_size * args.reduction_stride;
-    }
     cub::StoreDirectBlocked(
         warp.meta_group_rank(),
         out + tile_y * args.reduction_stride + tile_x * BN,
@@ -247,12 +227,11 @@ __global__ void col_reduce_small(
 inline auto output_grid_for_col_reduce(
     const array& out,
     const cu::ColReduceArgs& args,
-    int bn,
-    int outer = 1) {
+    int bn) {
   int gx, gy = 1;
   size_t n_inner_blocks = cuda::ceil_div(args.reduction_stride, bn);
   size_t n_outer_blocks = out.size() / args.reduction_stride;
-  size_t n_blocks = n_outer_blocks * n_inner_blocks * outer;
+  size_t n_blocks = n_outer_blocks * n_inner_blocks;
   while (n_blocks / gy > INT32_MAX) {
     gy *= 2;
   }
@@ -298,8 +277,7 @@ void col_reduce_looped(
             0,
             indata,
             gpu_ptr<U>(out),
-            static_cast<cu::ColReduceArgs>(args),
-            out.size() / args.reduction_stride);
+            static_cast<cu::ColReduceArgs>(args));
       });
     });
   });
@@ -342,117 +320,6 @@ void col_reduce_small(
   });
 }
 
-void col_reduce_two_pass(
-    cu::CommandEncoder& encoder,
-    const array& in,
-    array& out,
-    Reduce::ReduceType reduce_type,
-    const std::vector<int>& axes,
-    const ReductionPlan& plan,
-    const cu::ColReduceArgs& args) {
-  // Allocate data for the output using in's layout to access them as
-  // contiguously as possible.
-  allocate_same_layout(out, in, axes, encoder);
-
-  // Allocate an intermediate array to hold the 1st pass result
-  constexpr int outer = 32;
-
-  Shape intermediate_shape;
-  intermediate_shape.push_back(outer);
-  intermediate_shape.insert(
-      intermediate_shape.end(), out.shape().begin(), out.shape().end());
-
-  Strides intermediate_strides;
-  intermediate_strides.push_back(out.size());
-  intermediate_strides.insert(
-      intermediate_strides.end(), out.strides().begin(), out.strides().end());
-
-  array intermediate(intermediate_shape, out.dtype(), nullptr, {});
-  auto [data_size, rc, cc] =
-      check_contiguity(intermediate_shape, intermediate_strides);
-  auto fl = out.flags();
-  fl.row_contiguous = rc;
-  fl.col_contiguous = cc;
-  fl.contiguous = true;
-  intermediate.set_data(
-      cu::malloc_async(intermediate.nbytes(), encoder),
-      data_size,
-      intermediate_strides,
-      fl,
-      allocator::free);
-
-  encoder.add_temporary(intermediate);
-  encoder.set_input_array(in);
-  encoder.set_output_array(intermediate);
-  dispatch_all_types(in.dtype(), [&](auto type_tag) {
-    dispatch_reduce_ops(reduce_type, [&](auto reduce_type_tag) {
-      dispatch_reduce_ndim(args.reduce_ndim, [&](auto reduce_ndim) {
-        using OP = MLX_GET_TYPE(reduce_type_tag);
-        using T = cuda_type_t<MLX_GET_TYPE(type_tag)>;
-        using U = typename cu::ReduceResult<OP, T>::type;
-        // Cub doesn't like const pointers for vectorized loads. (sigh)
-        T* indata = const_cast<T*>(gpu_ptr<T>(in));
-
-        constexpr int N_READS = 4;
-        constexpr int BM = 32;
-        constexpr int BN = 32;
-        dim3 grid = output_grid_for_col_reduce(out, args, BN, outer);
-        int blocks = BM * BN / N_READS;
-        auto kernel = cu::
-            col_reduce_looped<T, U, OP, reduce_ndim(), BM, BN, N_READS, outer>;
-        encoder.add_kernel_node(
-            kernel,
-            grid,
-            blocks,
-            0,
-            indata,
-            gpu_ptr<U>(intermediate),
-            static_cast<cu::ColReduceArgs>(args),
-            out.size() / args.reduction_stride);
-      });
-    });
-  });
-
-  // Prepare the reduction arguments for the 2nd pass
-  cu::ColReduceArgs second_args = args;
-  second_args.reduction_size = outer;
-  second_args.reduction_stride = out.size();
-  second_args.ndim = 0;
-  second_args.reduce_shape[0] = outer;
-  second_args.reduce_strides[0] = out.size();
-  second_args.reduce_ndim = 1;
-  second_args.non_col_reductions = 1;
-
-  encoder.set_input_array(intermediate);
-  encoder.set_output_array(out);
-  dispatch_all_types(intermediate.dtype(), [&](auto type_tag) {
-    dispatch_reduce_ops(reduce_type, [&](auto reduce_type_tag) {
-      dispatch_reduce_ndim(second_args.reduce_ndim, [&](auto reduce_ndim) {
-        using OP = MLX_GET_TYPE(reduce_type_tag);
-        using T = cuda_type_t<MLX_GET_TYPE(type_tag)>;
-        using U = typename cu::ReduceResult<OP, T>::type;
-
-        constexpr int N_READS = 4;
-        constexpr int BM = 32;
-        constexpr int BN = 32;
-        dim3 grid = output_grid_for_col_reduce(out, second_args, BN);
-        int blocks = BM * BN / N_READS;
-        auto kernel =
-            cu::col_reduce_looped<T, U, OP, reduce_ndim(), BM, BN, N_READS>;
-        encoder.add_kernel_node(
-            kernel,
-            grid,
-            blocks,
-            0,
-            gpu_ptr<T>(intermediate),
-            gpu_ptr<U>(out),
-            second_args,
-            second_args.reduction_stride);
-      });
-    });
-  });
-}
-
 void col_reduce(
     cu::CommandEncoder& encoder,
     const array& in,
@@ -467,18 +334,6 @@ void col_reduce(
   //   It is a general strided reduce. Each threadblock computes the output for
   //   a subrow of the fast moving axis. For instance 32 elements.
   //
-  // - col_reduce_small
-  //
-  //  It is a column reduce for small columns. Each thread loops over the whole
-  //  column without communicating with any other thread.
-  //
-  // - col_reduce_two_pass
-  //
-  //  It is a reduce for long columns. To increase parallelism, we split the
-  //  reduction in two passes. First we do a column reduce where many
-  //  threadblocks operate on different parts of the reduced axis. Then we
-  //  perform a final column reduce.
-  //
   // Notes: As in row reduce we opt to read as much in order as possible and
   //        leave transpositions as they are (contrary to our Metal backend).
   //
@@ -494,14 +349,6 @@ void col_reduce(
     return;
   }
 
-  // Long column with smallish row
-  size_t total_sums = args.non_col_reductions * args.reduction_size;
-  size_t approx_threads = out.size();
-  if (total_sums / approx_threads > 32) {
-    col_reduce_two_pass(encoder, in, out, reduce_type, axes, plan, args);
-    return;
-  }
-
   // Fallback col reduce
   col_reduce_looped(encoder, in, out, reduce_type, axes, plan, args);
 }

mlx/backend/cuda/utils.cpp

@@ -80,6 +80,7 @@ CudaGraph::CudaGraph(cu::Device& device) {
 }
 
 void CudaGraph::end_capture(cudaStream_t stream) {
+  assert(handle_ == nullptr);
   CHECK_CUDA_ERROR(cudaStreamEndCapture(stream, &handle_));
 }
 

mlx/backend/gpu/copy.cpp

@@ -7,6 +7,8 @@
 
 namespace mlx::core {
 
+void copy_gpu(const array& in, array& out, CopyType ctype, const Stream& s);
+
 void copy_gpu(const array& in, array& out, CopyType ctype) {
   copy_gpu(in, out, ctype, out.primitive().stream());
 }

mlx/backend/metal/allocator.cpp

@@ -149,9 +149,7 @@ Buffer MetalAllocator::malloc(size_t size) {
       buf = device_->newBuffer(size, resource_options);
     }
     if (!buf) {
-      std::ostringstream msg;
-      msg << "[malloc] Unable to allocate " << size << " bytes.";
-      throw std::runtime_error(msg.str());
+      return Buffer{nullptr};
     }
     lk.lock();
     num_resources_++;
@@ -203,32 +201,6 @@ size_t MetalAllocator::size(Buffer buffer) const {
   return static_cast<MTL::Buffer*>(buffer.ptr())->length();
 }
 
-Buffer MetalAllocator::make_buffer(void* ptr, size_t size) {
-  auto buf = device_->newBuffer(ptr, size, resource_options, nullptr);
-  if (!buf) {
-    return Buffer{nullptr};
-  }
-  std::unique_lock lk(mutex_);
-  residency_set_.insert(buf);
-  active_memory_ += buf->length();
-  peak_memory_ = std::max(peak_memory_, active_memory_);
-  num_resources_++;
-  return Buffer{static_cast<void*>(buf)};
-}
-
-void MetalAllocator::release(Buffer buffer) {
-  auto buf = static_cast<MTL::Buffer*>(buffer.ptr());
-  if (buf == nullptr) {
-    return;
-  }
-  std::unique_lock lk(mutex_);
-  active_memory_ -= buf->length();
-  num_resources_--;
-  lk.unlock();
-  auto pool = metal::new_scoped_memory_pool();
-  buf->release();
-}
-
 MetalAllocator& allocator() {
   // By creating the |allocator_| on heap, the destructor of MetalAllocator
   // will not be called on exit and buffers in the cache will be leaked. This

mlx/backend/metal/allocator.h

@@ -21,9 +21,6 @@ class MetalAllocator : public allocator::Allocator {
   virtual Buffer malloc(size_t size) override;
   virtual void free(Buffer buffer) override;
   virtual size_t size(Buffer buffer) const override;
-  virtual Buffer make_buffer(void* ptr, size_t size) override;
-  virtual void release(Buffer buffer) override;
-
   size_t get_active_memory() {
     return active_memory_;
   };

mlx/backend/no_gpu/allocator.cpp

@@ -25,7 +25,6 @@ class CommonAllocator : public Allocator {
   virtual Buffer malloc(size_t size) override;
   virtual void free(Buffer buffer) override;
   virtual size_t size(Buffer buffer) const override;
-
   size_t get_active_memory() const {
     return active_memory_;
   };

python/mlx/_distributed_utils/common.py

@@ -1,6 +1,5 @@
 # Copyright © 2025 Apple Inc.
 
-import argparse
 import ipaddress
 import json
 import sys
@@ -17,14 +16,6 @@ class Host:
     rdma: list[Optional[str]]
 
 
-class OptionalBoolAction(argparse.Action):
-    def __call__(self, parser, namespace, values, option_string=None):
-        if option_string.startswith("--no-"):
-            setattr(namespace, self.dest, False)
-        else:
-            setattr(namespace, self.dest, True)
-
-
 def positive_number(x):
     x = int(x)
     if x <= 0:
@@ -35,7 +26,6 @@ def positive_number(x):
 def log(verbose, *args, **kwargs):
     if not verbose:
         return
-    kwargs["file"] = sys.stderr
     print("\033[32m[INFO]", *args, "\033[0m", **kwargs)
 
 
@@ -60,7 +50,7 @@ def parse_hostlist(parser, hostlist, repeats):
         except ValueError:
             ips = []
         for i in range(repeats):
-            hosts.append(Host(i, h, ips, []))
+            hosts.append(Host(i, h, ips))
     return hosts
 
 

python/mlx/_distributed_utils/config.py

@@ -1,570 +0,0 @@
-# Copyright © 2025 Apple Inc.
-
-import argparse
-import json
-import shlex
-import sys
-import threading
-from collections import defaultdict
-from dataclasses import dataclass
-from subprocess import DEVNULL, run
-from typing import Optional
-
-import mlx.core as mx
-
-from .common import (
-    Host,
-    OptionalBoolAction,
-    log,
-    log_error,
-    parse_hostfile,
-    parse_hostlist,
-)
-
-
-@dataclass
-class SSHInfo:
-    can_ssh: bool
-    has_sudo: bool
-
-    def __bool__(self):
-        return self.can_ssh
-
-
-@dataclass
-class ThunderboltPort:
-    iface: str
-    uuid: str
-    connected_to: Optional[str]
-
-
-@dataclass
-class ThunderboltHost:
-    name: str
-    ports: list[ThunderboltPort]
-
-
-def add_ethernet_ips(hosts, verbose=False):
-    # Get the ips for each host
-    for h in hosts:
-        log(verbose, "Getting the ip from", h.ssh_hostname)
-        h.ips.append(
-            run(
-                ["ssh", h.ssh_hostname, "ipconfig", "getifaddr", "en0"],
-                capture_output=True,
-                text=True,
-            ).stdout.strip()
-        )
-
-
-def check_rdma(hosts, verbose=False):
-    # Check whether the hosts are capable of RDMA over thunderbolt
-    warn = False
-    for h in hosts:
-        log(verbose, "Checking that", h.ssh_hostname, "supports RDMA")
-        rdma_devs = (
-            run(["ssh", h.ssh_hostname, "ibv_devices"], capture_output=True, text=True)
-            .stdout.strip()
-            .split()
-        )
-        rdma_devs = [d for d in rdma_devs if d.startswith("rdma_")]
-        if not rdma_devs:
-            log_warning(h.ssh_hostname, "does not seem to have RDMA enabled")
-            warn = True
-
-    if warn:
-        log_warning()
-        log_warning(
-            "Some of the hosts don't have RDMA enabled or they don't support RDMA."
-        )
-        log_warning()
-        log_warning(
-            "See https://ml-explore.github.io/mlx/build/html/usage/distributed.html"
-        )
-        log_warning("for instructions on how to enable RDMA.")
-
-
-def can_auto_setup(hosts, sshinfo, auto_setup=False):
-    has_sudo = all(info.has_sudo for info in sshinfo)
-    if not has_sudo and auto_setup:
-        log_warning(
-            "Automatic setup requested but the following hosts do not have passwordless sudo"
-        )
-        for h, i in zip(hosts, sshinfo):
-            if not i.has_sudo:
-                log_warning(" - ", h.ssh_hostname)
-    return has_sudo
-
-
-class IPConfigurator:
-    def __init__(self, hosts, tb_hosts, uuid_reverse_index):
-        assigned = set()
-        ips = defaultdict(list)
-        ip0 = 0
-        ip1 = 0
-        for src_node, h in enumerate(tb_hosts):
-            for src_port, p in enumerate(h.ports):
-                if not p.connected_to:
-                    continue
-                if p.connected_to not in uuid_reverse_index:
-                    continue
-                if (src_node, src_port) in assigned:
-                    continue
-
-                dst_node, dst_port = uuid_reverse_index[p.connected_to]
-
-                ip_src = f"192.168.{ip0}.{ip1 + 1}"
-                ip_dst = f"192.168.{ip0}.{ip1 + 2}"
-                iface_src = p.iface
-                iface_dst = tb_hosts[dst_node].ports[dst_port].iface
-
-                ips[src_node, dst_node].append((iface_src, ip_src))
-                ips[dst_node, src_node].append((iface_dst, ip_dst))
-
-                assigned.add((src_node, src_port))
-                assigned.add((dst_node, dst_port))
-
-                ip1 += 4
-                if ip1 > 255:
-                    ip0 += 1
-                    ip1 = 0
-                if ip0 > 255:
-                    raise ValueError("Ran out of available local IPs")
-
-        self.ips = ips
-        self.hosts = hosts
-        self.tb_hosts = tb_hosts
-
-    def setup(self, verbose=False, auto_setup=False):
-        netmask = "255.255.255.252"
-        for i, (h, th) in enumerate(zip(self.hosts, self.tb_hosts)):
-            command = ""
-            command += "sudo ifconfig bridge0 down\n"
-            for j in range(len(self.hosts)):
-                if i == j or (i, j) not in self.ips:
-                    continue
-                for (iface, ip), (_, peer) in zip(self.ips[i, j], self.ips[j, i]):
-                    command += f"sudo ifconfig {iface} inet {ip} netmask {netmask}\n"
-                    command += f"sudo route change {peer} -interface {iface}\n"
-            if auto_setup:
-                print(f"Running auto setup for {h.ssh_hostname}")
-                command = command.strip().replace("\n", " ; ")
-                command = ["ssh", h.ssh_hostname, command]
-                log(verbose, shlex.join(command))
-                run(command)
-            else:
-                msg = f"Setup for {h.ssh_hostname}"
-                print(msg)
-                print("=" * len(msg))
-                print(command)
-                input("Enter to continue")
-            print()
-
-
-def parse_hardware_ports(ports_string):
-    ports = {}
-    port_name = None
-    for l in ports_string.decode("utf-8").split("\n"):
-        if l.startswith("Hardware Port:"):
-            port_name = l.strip()[15:]
-        elif l.startswith("Device:"):
-            ports[port_name] = l.strip()[8:]
-            port_name = None
-    return ports
-
-
-def extract_connectivity(hosts, verbose):
-    # Extract the current connectivity from the remote hosts
-    thunderbolt_connections = []
-    for h in hosts:
-        log(verbose, "Getting connectivity from", h.ssh_hostname)
-        thunderbolt_connections.append(
-            json.loads(
-                run(
-                    [
-                        "ssh",
-                        h.ssh_hostname,
-                        "system_profiler",
-                        "SPThunderboltDataType",
-                        "-json",
-                    ],
-                    capture_output=True,
-                ).stdout
-            )
-        )
-    interface_maps = []
-    for h in hosts:
-        log(verbose, "Getting interface names from", h.ssh_hostname)
-        interface_maps.append(
-            parse_hardware_ports(
-                run(
-                    [
-                        "ssh",
-                        h.ssh_hostname,
-                        "networksetup",
-                        "-listallhardwareports",
-                    ],
-                    capture_output=True,
-                ).stdout
-            )
-        )
-
-    # Parse the connectivity into some simple dataclasses
-    tb_hosts = []
-    for c, iface_map in zip(thunderbolt_connections, interface_maps):
-        name = ""
-        ports = []
-        for t in c["SPThunderboltDataType"]:
-            uuid = t.get("domain_uuid_key")
-            if uuid is None:
-                continue
-            name = t["device_name_key"]
-            tag = t["receptacle_1_tag"]["receptacle_id_key"]
-            items = t.get("_items", [])
-            connected_items = [item for item in items if "domain_uuid_key" in item]
-            connected_to = (
-                connected_items[0]["domain_uuid_key"] if connected_items else None
-            )
-            iface = iface_map[f"Thunderbolt {tag}"]
-            ports.append(ThunderboltPort(iface, uuid, connected_to))
-        tb_hosts.append(ThunderboltHost(name, sorted(ports, key=lambda x: x.iface)))
-
-    # Create a reverse index to be able to map uuids to (host, port) quickly
-    uuid_reverse_index = {}
-    for i, h in enumerate(tb_hosts):
-        for j, p in enumerate(h.ports):
-            uuid_reverse_index[p.uuid] = (i, j)
-
-    return tb_hosts, uuid_reverse_index
-
-
-def make_connectivity_matrix(tb_hosts, uuid_reverse_index):
-    connectivity = []
-    for i, h in enumerate(tb_hosts):
-        c = [0] * len(tb_hosts)
-        for p in h.ports:
-            if p.connected_to in uuid_reverse_index:
-                j, _ = uuid_reverse_index[p.connected_to]
-                c[j] += 1
-        connectivity.append(c)
-    return connectivity
-
-
-def tb_connectivity_to_dot(hosts, tb_hosts, uuid_reverse_index):
-    # Make ids per node
-    names = []
-    for i in range(len(tb_hosts)):
-        n = ""
-        j = i
-        while True:
-            n += chr(97 + j % 26)
-            j //= 26
-            if j == 0:
-                break
-        names.append(n)
-
-    print("graph G {")
-    print("  node [shape=rectangle];")
-    for i, h in enumerate(hosts):
-        print(f'  {names[i]} [label="{h.ssh_hostname}"];')
-    for i, h in enumerate(tb_hosts):
-        for p in h.ports:
-            if not p.connected_to:
-                continue
-            dst = uuid_reverse_index[p.connected_to]
-            if dst[0] < i:
-                continue
-            print(f"  {names[i]} -- {names[dst[0]]}", end="")
-            print(f' [label="{p.iface}/{tb_hosts[dst[0]].ports[dst[1]].iface}"]')
-    print("}")
-
-
-def extract_rings(connectivity):
-    rings = []
-    existing_rings = set()
-    num_nodes = len(connectivity)
-
-    def dfs(start_node, node, path, visited):
-        path.append(node)
-        visited.add(node)
-        for j in range(num_nodes):
-            if connectivity[node][j] <= 0:
-                continue
-            if j == start_node:
-                yield path[:]
-            if j not in visited:
-                yield from dfs(start_node, j, path, visited)
-        path.pop()
-        visited.remove(node)
-
-    for start in range(num_nodes):
-        for r in dfs(start, start, [], set()):
-            cnt = min(connectivity[r[i]][r[(i + 1) % len(r)]] for i in range(len(r)))
-            rkey = tuple(sorted(r))
-            if rkey not in existing_rings:
-                rings.append((r, cnt))
-                existing_rings.add(rkey)
-
-    return sorted(rings, key=lambda x: -len(x[0]))
-
-
-def check_valid_mesh(hosts, connectivity, strict=True):
-    num_nodes = len(connectivity)
-    for i in range(num_nodes):
-        for j in range(num_nodes):
-            if i == j:
-                continue
-            if connectivity[i][j] <= 0:
-                if strict:
-                    log_error(
-                        f"Incomplete mesh, {hosts[i].ssh_hostname} is not connected to {hosts[j].ssh_hostname}"
-                    )
-                    log_error()
-                    log_error("Try passing --dot to visualize the connectivity")
-                    sys.exit(1)
-                else:
-                    return False
-    return True
-
-
-def check_ssh_connections(hosts):
-    results = [None] * len(hosts)
-
-    def _check(hostname, i):
-        info = SSHInfo(False, False)
-        results[i] = info
-
-        # Check for ssh
-        result = run(
-            [
-                "ssh",
-                "-o",
-                "BatchMode=yes",
-                "-o",
-                "ConnectTimeout=5",
-                hostname,
-                "echo",
-                "success",
-            ],
-            stdout=DEVNULL,
-            stderr=DEVNULL,
-        )
-        info.can_ssh = result.returncode == 0
-        if not info.can_ssh:
-            return
-
-        # Check for sudo
-        result = run(
-            [
-                "ssh",
-                "-o",
-                "BatchMode=yes",
-                "-o",
-                "ConnectTimeout=5",
-                hostname,
-                "sudo",
-                "ls",
-            ],
-            stdout=DEVNULL,
-            stderr=DEVNULL,
-        )
-        info.has_sudo = result.returncode == 0
-
-    threads = [
-        threading.Thread(target=_check, args=(h.ssh_hostname, i))
-        for i, h in enumerate(hosts)
-    ]
-    for t in threads:
-        t.start()
-    for t in threads:
-        t.join()
-
-    if not all(results):
-        log_error("Could not ssh to the following hosts:")
-        for i, h in enumerate(hosts):
-            if not results[i]:
-                log_error("  - ", h.ssh_hostname)
-        log_error()
-        log_error("Maybe they are not set-up for password-less ssh?")
-        sys.exit(1)
-
-    return results
-
-
-def prepare_ethernet_hostfile(args, hosts):
-    log(args.verbose, f"Preparing an ethernet hostfile")
-    add_ethernet_ips(hosts, args.verbose)
-
-    hostfile = []
-    for h in hosts:
-        hostfile.append(dict(ssh=h.ssh_hostname, ips=h.ips))
-
-    if args.output_hostfile:
-        with open(args.output_hostfile, "w") as f:
-            json.dump(hostfile, f, indent=4)
-    else:
-        print("Hostfile")
-        print("========")
-        print(json.dumps(hostfile, indent=4))
-
-
-def configure_ring(args, hosts, ips, ring, sshinfo):
-    log(args.verbose, "Prepare a ring hostfile")
-    ring, count = ring
-    hostfile = []
-    for i, node in enumerate(ring):
-        h = hosts[node]
-        peer = ring[i - 1]
-        hostfile.append(
-            {
-                "ssh": h.ssh_hostname,
-                "ips": [ips.ips[node, peer][c][1] for c in range(count)],
-                "rdma": [],
-            }
-        )
-
-    has_sudo = can_auto_setup(hosts, sshinfo, args.auto_setup)
-    ips.setup(verbose=args.verbose, auto_setup=args.auto_setup and has_sudo)
-
-    if args.output_hostfile:
-        with open(args.output_hostfile, "w") as f:
-            json.dump(hostfile, f, indent=4)
-    else:
-        print("Hostfile")
-        print("========")
-        print(json.dumps(hostfile, indent=4))
-
-
-def configure_jaccl(args, hosts, ips, sshinfo):
-    log(args.verbose, "Prepare a jaccl hostfile")
-    check_rdma(hosts, args.verbose)
-    add_ethernet_ips(hosts, args.verbose)
-
-    hostfile = []
-    for i, h in enumerate(hosts):
-        rdma = []
-        for j in range(len(hosts)):
-            if i == j:
-                rdma.append(None)
-            else:
-                rdma.append(f"rdma_{ips.ips[i, j][0][0]}")
-        hostfile.append({"ssh": h.ssh_hostname, "ips": h.ips, "rdma": rdma})
-
-    has_sudo = can_auto_setup(hosts, sshinfo, args.auto_setup)
-    ips.setup(verbose=args.verbose, auto_setup=args.auto_setup and has_sudo)
-
-    if args.output_hostfile:
-        with open(args.output_hostfile, "w") as f:
-            json.dump(hostfile, f, indent=4)
-    else:
-        print("Hostfile")
-        print("========")
-        print(json.dumps(hostfile, indent=4))
-
-
-def prepare_tb_hostfile(args, hosts, sshinfo):
-    log(args.verbose, f"Preparing for communication over thunderbolt")
-    tb_hosts, uuid_reverse_index = extract_connectivity(hosts, args.verbose)
-
-    if args.dot:
-        tb_connectivity_to_dot(hosts, tb_hosts, uuid_reverse_index)
-        return
-
-    ips = IPConfigurator(hosts, tb_hosts, uuid_reverse_index)
-    connectivity = make_connectivity_matrix(tb_hosts, uuid_reverse_index)
-
-    if args.backend is None:
-        rings = extract_rings(connectivity)
-        has_mesh = check_valid_mesh(hosts, connectivity, False)
-        has_ring = len(rings) > 0 and len(rings[0][0]) == len(hosts)
-
-        if not has_ring and not has_mesh:
-            log_error("Neither thunderbolt mesh nor ring found.")
-            log_error("Perhaps run with --dot to generate a plot of the connectivity.")
-            sys.exit(1)
-
-        elif has_ring:
-            configure_ring(args, hosts, ips, rings[0], sshinfo)
-
-        else:
-            configure_jaccl(args, hosts, ips, sshinfo)
-
-    elif args.backend == "ring":
-        rings = extract_rings(connectivity)
-        has_ring = len(rings) > 0 and len(rings[0][0]) == len(hosts)
-        if not has_ring:
-            log_error("Could not find a full ring.")
-            log_error()
-            log_error("Try passing --dot to visualize the connectivity")
-            if len(rings) > 0:
-                log_error("Rings found:")
-                for r in rings:
-                    log_error(f" - {','.join(hosts[i].ssh_hostname for i in r)}")
-            sys.exit(1)
-        configure_ring(args, hosts, ips, rings[0], sshinfo)
-
-    elif args.backend == "jaccl":
-        check_valid_mesh(hosts, connectivity)
-        configure_jaccl(args, hosts, ips, sshinfo)
-
-
-def main():
-    parser = argparse.ArgumentParser(
-        description="Configure remote machines for use with MLX distributed"
-    )
-    parser.add_argument(
-        "--verbose", action="store_true", help="Print debug messages in stdout"
-    )
-    parser.add_argument(
-        "--hosts", default="127.0.0.1", help="A comma separated list of hosts"
-    )
-    parser.add_argument("--hostfile", help="The file containing the hosts")
-    parser.add_argument(
-        "--over",
-        choices=["thunderbolt", "ethernet"],
-        default="thunderbolt",
-        help="What type of connectivity to configure",
-        required=True,
-    )
-    parser.add_argument(
-        "--output-hostfile", help="If provided, save the hostfile to this path"
-    )
-    parser.add_argument(
-        "--auto-setup",
-        "--no-auto-setup",
-        action=OptionalBoolAction,
-        nargs=0,
-        dest="auto_setup",
-        default=None,
-    )
-    parser.add_argument(
-        "--dot", action="store_true", help="Output the topology in DOT format and exit"
-    )
-    parser.add_argument(
-        "--backend",
-        choices=["ring", "jaccl"],
-        default=None,
-        help="Which distributed backend to configure",
-    )
-    args = parser.parse_args()
-
-    if args.hostfile is not None:
-        hosts = parse_hostfile(parser, args.hostfile)
-    else:
-        hosts = parse_hostlist(parser, args.hosts, 1)
-
-    # Check that we can ssh
-    log(
-        args.verbose,
-        f"Checking for ssh access for {', '.join(h.ssh_hostname for h in hosts)}",
-    )
-    sshinfo = check_ssh_connections(hosts)
-
-    # Prepare a hostfile for communication over ethernet using the ips of the
-    # provided hostnames
-    if args.over == "ethernet":
-        prepare_ethernet_hostfile(args, hosts)
-
-    # Configure the macs for communication over thunderbolt, both via RDMA and IP
-    else:
-        prepare_tb_hostfile(args, hosts, sshinfo)

python/mlx/_distributed_utils/distributed_run.py

@@ -0,0 +1,911 @@
+# Copyright © 2025 Apple Inc.
+
+import argparse
+import base64
+import ipaddress
+import json
+import os
+import platform
+import shlex
+import shutil
+import sys
+import tempfile
+import threading
+import time
+from collections import Counter
+from dataclasses import dataclass
+from pathlib import Path
+from queue import Empty as QueueEmpty
+from queue import Queue
+from select import select
+from subprocess import PIPE, Popen, run
+from typing import Optional
+
+import mlx.core as mx
+
+
+@dataclass
+class Host:
+    rank: int
+    ssh_hostname: str
+    ips: list[str]
+
+
+@dataclass
+class ThunderboltPort:
+    iface: str
+    uuid: str
+    connected_to: Optional[str]
+
+
+@dataclass
+class ThunderboltHost:
+    name: str
+    ports: list[ThunderboltPort]
+
+
+def parse_hardware_ports(ports_string):
+    ports = {}
+    port_name = None
+    for l in ports_string.decode("utf-8").split("\n"):
+        if l.startswith("Hardware Port:"):
+            port_name = l.strip()[15:]
+        elif l.startswith("Device:"):
+            ports[port_name] = l.strip()[8:]
+            port_name = None
+    return ports
+
+
+def get_num_nvidia_gpus():
+    result = run(["nvidia-smi", "-L"], capture_output=True, text=True, check=True)
+    return len(result.stdout.strip().split("\n"))
+
+
+def extract_rings(hosts, index):
+    def usable_port(i, j, used_ports):
+        return (i, j) not in used_ports and hosts[i].ports[j].connected_to is not None
+
+    def dfs(start_node, node, path, visited, used_ports):
+        path.append(node)
+        visited.add(node)
+        for j, p in enumerate(hosts[node].ports):
+            if not usable_port(node, j, used_ports):
+                continue
+            next_node, _ = index[p.connected_to]
+            if next_node == start_node:
+                yield path[:]
+            if next_node not in visited:
+                yield from dfs(start_node, next_node, path, visited, used_ports)
+        path.pop()
+        visited.remove(node)
+
+    # Concretize maps the found cycle to real thunderbolt ports. It also adds
+    # those ports to the used set so next cycles can't use them again.
+    def concretize(cycle, used_ports):
+        concrete_path = []
+        for n1, n2 in zip(cycle, cycle[1:] + cycle[:1]):
+            for j, p in enumerate(hosts[n1].ports):
+                if not usable_port(n1, j, used_ports):
+                    continue
+                n2_hat, nj = index[p.connected_to]
+                if n2 == n2_hat:
+                    concrete_path.append(((n1, j), (n2, nj)))
+                    used_ports.add((n1, j))
+                    used_ports.add((n2, nj))
+                    break
+            if concrete_path[-1][0][0] != n1:
+                raise RuntimeError("Couldn't concretize the cycle")
+        return concrete_path
+
+    # Normalize tries to ensure that the cycles have the same direction so we can
+    # use them together. We achieve this by selecting the direction such that
+    # the smallest rank hosts connect to larger rank hosts.
+    def normalize(path):
+        small_to_large = sum(1 for p in path if p[0][0] < p[1][0])
+        if small_to_large > len(path) - small_to_large:
+            return path
+        else:
+            return [(p[1], p[0]) for p in path]
+
+    rings = []
+    used_ports = set()
+    for start_node in range(len(hosts)):
+        while True:
+            ring = []
+            for r in dfs(start_node, start_node, [], set(), used_ports):
+                if len(r) > len(ring):
+                    ring = r
+                # Break early since we won't find a bigger ring no matter what
+                if len(ring) == len(hosts):
+                    break
+            if not ring:
+                break
+            try:
+                rings.append(normalize(concretize(ring, used_ports)))
+            except RuntimeError:
+                if len(rings) > 0:
+                    return rings
+                raise
+
+    return rings
+
+
+def positive_number(x):
+    x = int(x)
+    if x <= 0:
+        raise ValueError("Number should be positive")
+    return x
+
+
+def log(verbose, *args, **kwargs):
+    if not verbose:
+        return
+    print("\033[32m[INFO]", *args, "\033[0m", **kwargs)
+
+
+def log_warning(*args, **kwargs):
+    kwargs["file"] = sys.stderr
+    print("\033[33m[WARN]", *args, "\033[0m", **kwargs)
+
+
+def log_error(*args, **kwargs):
+    kwargs["file"] = sys.stderr
+    print("\033[31m[ERROR]", *args, "\033[0m", **kwargs)
+
+
+def parse_hostfile(parser, hostfile):
+    """Parse the json hostfile that contains both the hostnames to ssh into and
+    the ips to communicate over when using the ring backend.
+
+    Example:
+
+        [
+            {"ssh": "hostname1", "ips": ["123.123.123.1"]},
+            {"ssh": "hostname2", "ips": ["123.123.123.2"]},
+            ...
+            {"ssh": "hostnameN", "ips": ["123.123.123.N"]},
+        ]
+
+    Args:
+        hostfile (str): The path to the json file containing the host
+            information
+    """
+    hostfile = Path(hostfile)
+    if not hostfile.exists():
+        parser.error(f"Hostfile {str(hostfile)} doesn't exist")
+
+    try:
+        hosts = []
+        with open(hostfile) as f:
+            for i, h in enumerate(json.load(f)):
+                hosts.append(Host(i, h["ssh"], h.get("ips", [])))
+        return hosts
+    except Exception as e:
+        parser.error(f"Failed to parse hostfile {str(hostfile)} ({str(e)})")
+
+
+def parse_hostlist(parser, hostlist, repeats):
+    hosts = []
+    for i, h in enumerate(hostlist.split(",")):
+        if h == "":
+            raise ValueError("Hostname cannot be empty")
+        try:
+            ipaddress.ip_address(h)
+            ips = [h]
+        except ValueError:
+            ips = []
+        for i in range(repeats):
+            hosts.append(Host(i, h, ips))
+    return hosts
+
+
+def make_monitor_script(rank, hostfile, cwd, env, command, verbose):
+    # Imports that are used throughout
+    script = ""
+    script += "import os\n"
+    script += "import sys\n"
+    script += "import tempfile\n"
+    script += "from pathlib import Path\n"
+
+    # Write the PID to a file so we can kill the process if needed
+    script += "_, pidfile = tempfile.mkstemp() \n"
+    script += "open(pidfile, 'w').write(str(os.getpid()))\n"
+    script += "print(pidfile, flush=True)\n"
+
+    # Change the working directory if one was requested. Otherwise attempt to
+    # change to the current one but don't fail if it wasn't possible.
+    d = cwd or os.getcwd()
+    script += f"if Path({repr(d)}).exists():\n"
+    script += f"    os.chdir({repr(d)})\n"
+    if cwd is not None:
+        script += "else:\n"
+        script += (
+            f"    print('Failed to change directory to', {repr(d)}, file=sys.stderr)\n"
+        )
+        script += f"    sys.exit(1)\n"
+
+    # Add the environment variables that were given to us
+    script += "env = dict(os.environ)\n"
+    for e in env:
+        key, *value = e.split("=", maxsplit=1)
+        value = shlex.quote(value[0]) if len(value) > 0 else ""
+        if not all(c.isalnum() or c == "_" for c in key):
+            log_warning(f"'{e}' is an invalid environment variable so it is ignored")
+            continue
+        script += f"env[{repr(key)}] = {repr(value)}\n"
+
+    # Add the environment variables to enable the ring distributed backend
+    if hostfile != "":
+        script += "_, hostfile = tempfile.mkstemp()\n"
+        script += "with open(hostfile, 'w') as f:\n"
+        script += f"    f.write({repr(hostfile)})\n"
+        if verbose:
+            script += "env['MLX_RING_VERBOSE'] = '1'\n"
+        script += "env['MLX_HOSTFILE'] = hostfile\n"
+        script += f"env['MLX_RANK'] = '{rank}'\n"
+        script += "\n"
+
+    # Replace the process with the script
+    script += f"command = [{','.join(map(repr, command))}]\n"
+    script += "os.execve(command[0], command, env)\n"
+
+    return script
+
+
+def launch_ring(parser, hosts, args, command):
+    stop = False
+    exit_codes = [None] * len(hosts)
+
+    def node_thread(rank, host, hostfile, input_queue):
+        is_local = host == "127.0.0.1"
+        script = make_monitor_script(
+            rank, hostfile, args.cwd, args.env, command, args.verbose
+        )
+        script_b64 = base64.b64encode(script.encode()).decode()
+        cmd = f'{sys.executable} -c "import base64; exec(base64.b64decode(\\"{script_b64}\\"));"'
+        if not is_local:
+            cmd = f"ssh {host} '{cmd}'"
+        p = Popen(
+            cmd,
+            shell=True,
+            stdin=PIPE,
+            stdout=PIPE,
+            stderr=PIPE,
+        )
+        os.set_blocking(p.stdout.fileno(), False)
+        os.set_blocking(p.stderr.fileno(), False)
+        os.set_blocking(p.stdin.fileno(), False)
+
+        # Repeat the stdout and stderr to the local machine
+        to_read = [p.stdout.fileno(), p.stderr.fileno()]
+        to_write = [p.stdin.fileno(), sys.stdout.fileno(), sys.stderr.fileno()]
+        pidfile = ""
+        stdin_buffer = b""
+        stdout_buffer = b""
+        stderr_buffer = b""
+        while p.poll() is None:
+            try:
+                stdin_buffer += input_queue.get_nowait()
+            except QueueEmpty:
+                pass
+            rlist, wlist, _ = select(to_read, to_write, [], 1.0)
+            for fd in rlist:
+                msg = os.read(fd, 8192).decode(errors="ignore")
+
+                # Fetch the PID file first if we haven't already
+                if pidfile == "":
+                    pidfile, *msg = msg.split("\n", maxsplit=1)
+                    msg = msg[0] if msg else ""
+
+                is_stdout = fd == p.stdout.fileno()
+                if is_stdout:
+                    stdout_buffer += msg.encode()
+                else:
+                    stderr_buffer += msg.encode()
+            for fd in wlist:
+                if fd == p.stdin.fileno() and len(stdin_buffer) > 0:
+                    n = os.write(fd, stdin_buffer)
+                    stdin_buffer = stdin_buffer[n:]
+                elif fd == sys.stdout.fileno() and len(stdout_buffer) > 0:
+                    n = os.write(fd, stdout_buffer)
+                    stdout_buffer = stdout_buffer[n:]
+                elif fd == sys.stderr.fileno() and len(stderr_buffer) > 0:
+                    n = os.write(fd, stderr_buffer)
+                    stderr_buffer = stderr_buffer[n:]
+            if stop:
+                p.terminate()
+                break
+        p.wait()
+        exit_codes[rank] = p.returncode
+
+        # Kill the remote program if possible
+        cmd = ""
+        cmd += f"pid=$(cat {pidfile}); "
+        cmd += "if ps -p $pid >/dev/null; then "
+        cmd += "    kill $pid; "
+        cmd += "    echo 1; "
+        cmd += "else "
+        cmd += "    echo 0; "
+        cmd += "fi; "
+        cmd += f"rm {pidfile}"
+        if not is_local:
+            cmd = f"ssh {host} '{cmd}'"
+        c = run(cmd, check=True, shell=True, capture_output=True, text=True)
+        if c.stdout.strip() == "1":
+            log_warning(f"Node with rank {rank} was killed")
+        elif p.returncode != 0:
+            log_warning(f"Node with rank {rank} exited with code {p.returncode}")
+        else:
+            log(args.verbose, f"Node with rank {rank} completed")
+
+    if all(len(h.ips) == 0 for h in hosts):
+        parser.error(
+            "The ring backend requires IPs to be provided instead of hostnames"
+        )
+
+    port = args.starting_port
+    ring_hosts = []
+    for h in hosts:
+        node = []
+        for ip in h.ips:
+            for i in range(args.connections_per_ip):
+                node.append(f"{ip}:{port}")
+                port += 1
+        ring_hosts.append(node)
+    hostfile = json.dumps(ring_hosts) if len(ring_hosts) > 1 else ""
+
+    log(args.verbose, "Running", shlex.join(command))
+
+    input_queues = []
+    threads = []
+    for i, h in enumerate(hosts):
+        if i + 1 == len(hosts):
+            time.sleep(1.0)
+        input_queues.append(Queue())
+        t = threading.Thread(
+            target=node_thread, args=(i, h.ssh_hostname, hostfile, input_queues[-1])
+        )
+        t.start()
+        threads.append(t)
+
+    os.set_blocking(sys.stdin.fileno(), False)
+    while not stop:
+        rlist, _, _ = select([sys.stdin.fileno()], [], [], 1.0)
+        for fd in rlist:
+            stdin_buffer = os.read(fd, 8192)
+            for q in input_queues:
+                q.put(stdin_buffer)
+        if any(t.is_alive() for t in threads):
+            for i, t in enumerate(threads):
+                if not t.is_alive():
+                    if exit_codes[i] != 0:
+                        stop = True
+                        break
+        else:
+            break
+    for t in threads:
+        t.join()
+
+
+def get_mpi_libname():
+    try:
+        ompi_info = run(["which", "ompi_info"], check=True, capture_output=True)
+        ompi_info = ompi_info.stdout.strip().decode()
+
+        if platform.system() == "Darwin":
+            otool_output = run(
+                ["otool", "-L", ompi_info], check=True, capture_output=True
+            )
+        else:
+            otool_output = run(["ldd", ompi_info], check=True, capture_output=True)
+        otool_output = otool_output.stdout.decode()
+
+        # StopIteration if not found
+        libmpi_line = next(
+            filter(lambda line: "libmpi" in line, otool_output.splitlines())
+        )
+        return libmpi_line.strip().split()[0].removeprefix("@rpath/")
+    except:
+        return None
+
+
+def launch_mpi(parser, hosts, args, command):
+    mpirun = run(["which", "mpirun"], check=True, capture_output=True)
+    mpirun = mpirun.stdout.strip().decode()
+
+    # Compatibility with homebrew and pip installs
+    mpi_libname = get_mpi_libname()
+    if mpi_libname is not None:
+        dyld = Path(mpirun).parent.parent / "lib"
+        args.env = [
+            f"DYLD_LIBRARY_PATH={str(dyld)}",
+            f"MLX_MPI_LIBNAME={mpi_libname}",
+        ] + args.env
+
+    log(args.verbose, f"Using '{mpirun}'")
+    with tempfile.NamedTemporaryFile(mode="w") as f:
+        hosts = Counter((h.ssh_hostname for h in hosts))
+        for h, n in hosts.items():
+            print(f"{h} slots={n}", file=f)
+        f.flush()
+
+        cmd = [
+            mpirun,
+            "--output",
+            ":raw",  # do not line buffer output
+            "--hostfile",
+            f.name,
+            *(["-cwd", args.cwd] if args.cwd else []),
+            *sum((["-x", e] for e in args.env), []),
+            *sum([shlex.split(arg) for arg in args.mpi_arg], []),
+            "--",
+            *command,
+        ]
+        log(args.verbose, "Running", " ".join(cmd))
+        try:
+            run(cmd)
+        except KeyboardInterrupt:
+            pass
+
+
+def launch_nccl(parser, hosts, args, command):
+    master_host = hosts[0].ips[0]
+
+    if master_host != "127.0.0.1":
+        raise ValueError("The NCCL backend only supports localhost for now.")
+    master_port = args.nccl_port
+    world_size = len(hosts)
+
+    base_env = os.environ.copy()
+    base_env.update(
+        {
+            "NCCL_DEBUG": base_env.get(
+                "NCCL_DEBUG", "INFO" if args.verbose else "DEBUG"
+            ),
+            "NCCL_SOCKET_IFNAME": "lo",  # Use loopback for local communication
+            "NCCL_HOST_IP": master_host,
+            "NCCL_PORT": str(master_port),
+            "MLX_WORLD_SIZE": str(world_size),
+        }
+    )
+    procs = []
+    num_gpus = get_num_nvidia_gpus()
+    if num_gpus == 0:
+        raise RuntimeError("Cannot run NCCL backend with no GPUs.")
+    if args.repeat_hosts > num_gpus:
+        raise RuntimeError("NCCL requires a separate GPU per process.")
+
+    try:
+        for rank in range(world_size):
+            env = base_env.copy()
+            mlx_rank = str(rank % args.repeat_hosts)
+            env["MLX_RANK"] = mlx_rank
+            env["CUDA_VISIBLE_DEVICES"] = mlx_rank
+            p = Popen(command, env=env)
+            procs.append(p)
+
+        for p in procs:
+            ret = p.wait()
+            if ret != 0:
+                raise RuntimeError(f"Rank process exited with {ret}")
+
+    except (RuntimeError, KeyboardInterrupt) as err:
+        for p in procs:
+            if p.poll() is None:
+                try:
+                    p.kill()
+                except Exception:
+                    pass
+        raise
+
+
+def check_ssh_connections(hosts):
+    results = [False] * len(hosts)
+
+    def _check(hostname, i):
+        result = run(
+            [
+                "ssh",
+                "-o",
+                "BatchMode=yes",
+                "-o",
+                "ConnectTimeout=5",
+                hostname,
+                "echo",
+                "success",
+            ],
+            stdout=PIPE,
+            stderr=PIPE,
+        )
+        results[i] = result.returncode == 0
+
+    threads = [
+        threading.Thread(target=_check, args=(h.ssh_hostname, i))
+        for i, h in enumerate(hosts)
+    ]
+    for t in threads:
+        t.start()
+    for t in threads:
+        t.join()
+
+    if not all(results):
+        log_error("Could not ssh to the following hosts:")
+        for i, h in enumerate(hosts):
+            if not results[i]:
+                log_error("  - ", h.ssh_hostname)
+        log_error()
+        log_error("Maybe they are not set-up for password-less ssh?")
+        sys.exit(1)
+
+
+def prepare_tb_ring(args, hosts):
+    log(
+        args.verbose,
+        f"Preparing a thunderbolt ring for {', '.join(h.ssh_hostname for h in hosts)}",
+    )
+
+    # Check that we can ssh
+    check_ssh_connections(hosts)
+    if args.auto_setup and args.verbose:
+        log_warning(
+            "--auto-setup is requested which requires password-less sudo",
+            "on the remote hosts",
+        )
+
+    # Extract the current connectivity from the remote hosts
+    thunderbolt_connections = []
+    for h in hosts:
+        log(args.verbose, "Getting connectivity from", h.ssh_hostname)
+        thunderbolt_connections.append(
+            json.loads(
+                run(
+                    [
+                        "ssh",
+                        h.ssh_hostname,
+                        "system_profiler",
+                        "SPThunderboltDataType",
+                        "-json",
+                    ],
+                    capture_output=True,
+                ).stdout
+            )
+        )
+    interface_maps = []
+    for h in hosts:
+        log(args.verbose, "Getting interface names from", h.ssh_hostname)
+        interface_maps.append(
+            parse_hardware_ports(
+                run(
+                    [
+                        "ssh",
+                        h.ssh_hostname,
+                        "networksetup",
+                        "-listallhardwareports",
+                    ],
+                    capture_output=True,
+                ).stdout
+            )
+        )
+
+    # Parse the connectivity into some simple dataclasses
+    tb_hosts = []
+    for c, iface_map in zip(thunderbolt_connections, interface_maps):
+        name = ""
+        ports = []
+        for t in c["SPThunderboltDataType"]:
+            uuid = t.get("domain_uuid_key")
+            if uuid is None:
+                continue
+            name = t["device_name_key"]
+            tag = t["receptacle_1_tag"]["receptacle_id_key"]
+            items = t.get("_items", [])
+            connected_items = [item for item in items if "domain_uuid_key" in item]
+            connected_to = (
+                connected_items[0]["domain_uuid_key"] if connected_items else None
+            )
+            iface = iface_map[f"Thunderbolt {tag}"]
+            ports.append(ThunderboltPort(iface, uuid, connected_to))
+        tb_hosts.append(ThunderboltHost(name, sorted(ports, key=lambda x: x.iface)))
+
+    # Create a reverse index to be able to map uuids to (host, port) quickly
+    uuid_reverse_index = {}
+    for i, h in enumerate(tb_hosts):
+        for j, p in enumerate(h.ports):
+            uuid_reverse_index[p.uuid] = (i, j)
+
+    # Find the rings by simply walking and marking visited (host, port) tuples
+    # and keeping the largest rings greedily.
+    log(args.verbose, "Extracting rings from the parsed connectivity")
+    rings = extract_rings(tb_hosts, uuid_reverse_index)
+
+    # Just output a DOT graphical representation of the found rings
+    if args.dot:
+        names = []
+        for i in range(len(tb_hosts)):
+            n = ""
+            j = i
+            while True:
+                n += chr(97 + j % 26)
+                j //= 26
+                if j == 0:
+                    break
+            names.append(n)
+
+        print("graph G {")
+        print("  node [shape=rectangle];")
+        for i, h in enumerate(hosts):
+            print(f'  {names[i]} [label="{h.ssh_hostname}"];')
+        for r in rings:
+            for (i, _), (j, _) in r:
+                print(f"  {names[i]} -- {names[j]};")
+        print("}")
+        return
+
+    # Assign IPs to each interface such that the interfaces can communicate
+    ips = {}
+    pairs = {}
+    expecting = set()
+    ip0 = 0
+    ip1 = 0
+    netmask = "255.255.255.252"
+    for r in rings:
+        for a, b in r:
+            ips[a] = f"192.168.{ip0}.{ip1 + 1}"
+            ips[b] = f"192.168.{ip0}.{ip1 + 2}"
+            pairs[a] = b
+            pairs[b] = a
+            expecting.add(b)
+            ip1 += 4
+            if ip1 > 255:
+                ip0 += 1
+                ip1 = 0
+            if ip0 > 255:
+                raise ValueError("Ran out of available local IPs for the ring")
+
+    # Extract the host order from the first ring
+    hostmap = dict((r[0][0], r[1][0]) for r in rings[0])
+    first_host = min(hostmap.keys())
+    order = [first_host]
+    while hostmap[order[-1]] != first_host:
+        order.append(hostmap[order[-1]])
+
+    # Create the hostfile
+    hostfile = []
+    for i in order:
+        h = hosts[i]
+        host = {
+            "ssh": h.ssh_hostname,
+            "ips": [
+                ips[i, j]
+                for j, p in enumerate(tb_hosts[i].ports)
+                if (i, j) in expecting
+            ],
+        }
+        hostfile.append(host)
+
+    if not args.hostfile_only:
+        for i, h in enumerate(hosts):
+            command = ""
+            command += "sudo ifconfig bridge0 down\n"
+            for j, p in enumerate(tb_hosts[i].ports):
+                if (i, j) not in ips:
+                    continue
+                iface = p.iface
+                ip = ips[i, j]
+                peer = ips[pairs[i, j]]
+                command += f"sudo ifconfig {iface} inet {ip} netmask {netmask}\n"
+                command += f"sudo route change {peer} -interface {iface}\n"
+            if args.auto_setup:
+                print(f"Running auto setup for {h.ssh_hostname}")
+                command = command.strip().replace("\n", " && ")
+                command = ["ssh", h.ssh_hostname, command]
+                log(args.verbose, shlex.join(command))
+                run(command)
+            else:
+                msg = f"Setup for {h.ssh_hostname}"
+                print(msg)
+                print("=" * len(msg))
+                print(command)
+                input("Enter to continue")
+            print()
+
+    if args.output_hostfile:
+        with open(args.output_hostfile, "w") as f:
+            json.dump(hostfile, f, indent=4)
+    else:
+        print("Hostfile")
+        print("========")
+        print(json.dumps(hostfile, indent=4))
+
+
+def prepare_hostfile(args, hosts):
+    log(
+        args.verbose,
+        f"Preparing an ethernet hostfile for {', '.join(h.ssh_hostname for h in hosts)}",
+    )
+
+    # Check that we can ssh
+    check_ssh_connections(hosts)
+
+    # Get the ips for each host
+    for h in hosts:
+        log(args.verbose, "Getting the ip from", h.ssh_hostname)
+        h.ips.append(
+            run(
+                ["ssh", h.ssh_hostname, "ipconfig", "getifaddr", "en0"],
+                capture_output=True,
+                text=True,
+            ).stdout.strip()
+        )
+
+    hostfile = []
+    for h in hosts:
+        hostfile.append(dict(ssh=h.ssh_hostname, ips=h.ips))
+
+    if args.output_hostfile:
+        with open(args.output_hostfile, "w") as f:
+            json.dump(hostfile, f, indent=4)
+    else:
+        print("Hostfile")
+        print("========")
+        print(json.dumps(hostfile, indent=4))
+
+
+def distributed_config():
+    parser = argparse.ArgumentParser(
+        description="Configure remote machines for use with MLX distributed"
+    )
+    parser.add_argument(
+        "--verbose", action="store_true", help="Print debug messages in stdout"
+    )
+    parser.add_argument(
+        "--backend",
+        choices=["ring", "mpi", "nccl"],
+        default="nccl" if mx.cuda.is_available() else "ring",
+        help="Which distributed backend to configure",
+    )
+    parser.add_argument(
+        "--over",
+        choices=["thunderbolt", "ethernet"],
+        default="thunderbolt",
+        help="What type of connectivity to configure",
+    )
+    parser.add_argument(
+        "--hosts", default="127.0.0.1", help="A comma separated list of hosts"
+    )
+    parser.add_argument("--hostfile", help="The file containing the hosts")
+    parser.add_argument(
+        "--dot", action="store_true", help="Output the topology in DOT format and exit"
+    )
+    parser.add_argument(
+        "--hostfile-only", action="store_true", help="If set only compute the hostfile"
+    )
+    parser.add_argument(
+        "--output-hostfile", help="If provided, save the hostfile to this path"
+    )
+    parser.add_argument(
+        "--auto-setup",
+        action="store_true",
+        help="If set we will attempt to automatically configure the machines via ssh",
+    )
+    args = parser.parse_args()
+
+    if args.backend == "mpi" and args.over == "thunderbolt":
+        raise ValueError(
+            (
+                "The configuration of MPI over thunderbolt is "
+                "not supported yet by mlx.distributed_config"
+            )
+        )
+
+    if args.hostfile is not None:
+        hosts = parse_hostfile(parser, args.hostfile)
+    else:
+        hosts = parse_hostlist(parser, args.hosts, 1)
+
+    if args.over == "thunderbolt":
+        prepare_tb_ring(args, hosts)
+    else:
+        prepare_hostfile(args, hosts)
+
+
+def main():
+    parser = argparse.ArgumentParser(description="Launch an MLX distributed program")
+    parser.add_argument(
+        "--print-python",
+        action="store_true",
+        help="Print the path to the current python executable and exit",
+    )
+    parser.add_argument(
+        "--verbose", action="store_true", help="Print debug messages in stdout"
+    )
+    parser.add_argument(
+        "--hosts", default="127.0.0.1", help="A comma separated list of hosts"
+    )
+    parser.add_argument(
+        "--repeat-hosts",
+        "-n",
+        type=positive_number,
+        default=1,
+        help="Repeat each host a given number of times",
+    )
+    parser.add_argument("--hostfile", help="The file containing the hosts")
+    parser.add_argument(
+        "--backend",
+        choices=["ring", "mpi", "nccl", "jaccl"],
+        default="nccl" if mx.cuda.is_available() else "ring",
+        help="Which distributed backend to launch",
+    )
+    parser.add_argument(
+        "--env",
+        action="append",
+        default=[],
+        help="Set environment variables for the jobs",
+    )
+    parser.add_argument(
+        "--mpi-arg",
+        action="append",
+        default=[],
+        help="Arguments to pass directly to mpirun",
+    )
+    parser.add_argument(
+        "--connections-per-ip",
+        default=1,
+        type=int,
+        help="How many connections per ip to use for the ring backend",
+    )
+    parser.add_argument(
+        "--starting-port",
+        "-p",
+        type=int,
+        default=5000,
+        help="For the ring backend listen on this port increasing by 1 per rank and IP",
+    )
+    parser.add_argument(
+        "--cwd", help="Set the working directory on each node to the provided one"
+    )
+    parser.add_argument(
+        "--nccl-port",
+        type=int,
+        default=12345,
+        help="The port to use for the NCCL communication (only for nccl backend)",
+    )
+
+    args, rest = parser.parse_known_args()
+
+    if args.print_python:
+        print(sys.executable)
+        return
+
+    if len(rest) == 0:
+        parser.error("No script is provided")
+    if rest[0] == "--":
+        rest.pop(0)
+
+    # Try to extract a list of hosts and corresponding ips
+    if args.hostfile is not None:
+        hosts = parse_hostfile(parser, args.hostfile)
+    else:
+        hosts = parse_hostlist(parser, args.hosts, args.repeat_hosts)
+
+    # Check if the script is a file and convert it to a full path
+    if (script := Path(rest[0])).exists():
+        rest[0:1] = [sys.executable, str(script.resolve())]
+    elif (command := shutil.which(rest[0])) is not None:
+        rest[0] = command
+    else:
+        raise ValueError(f"Invalid script or command {rest[0]}")
+
+    # Launch
+    if args.backend == "ring":
+        launch_ring(parser, hosts, args, rest)
+    if args.backend == "mpi":
+        launch_mpi(parser, hosts, args, rest)
+    if args.backend == "nccl":
+        launch_nccl(parser, hosts, args, rest)
+    if args.backend == "jaccl":
+        launch_jaccl(parser, hosts, args, rest)
+
+
+if __name__ == "__main__":
+    main()

python/mlx/_distributed_utils/launch.py

@@ -45,11 +45,13 @@ class CommandProcess:
 
 
 class RemoteProcess(CommandProcess):
-    def __init__(self, rank, host, python, cwd, files, env, command):
+    def __init__(self, rank, host, cwd, files, env, command):
         is_local = host == "127.0.0.1"
-        cmd = RemoteProcess.make_launch_script(rank, cwd, files, env, command)
+        script = RemoteProcess.make_monitor_script(rank, cwd, files, env, command)
+        script_b64 = base64.b64encode(script.encode()).decode()
+        cmd = f'{sys.executable} -c "import base64; exec(base64.b64decode(\\"{script_b64}\\"));"'
         if not is_local:
-            cmd = f"ssh -tt -o LogLevel=QUIET {host} {shlex.quote(cmd)}"
+            cmd = f"ssh {host} '{cmd}'"
 
         self._host = host
         self._pidfile = None
@@ -57,7 +59,6 @@ class RemoteProcess(CommandProcess):
         self._process = Popen(
             cmd,
             shell=True,
-            executable="/bin/bash",
             stdin=PIPE,
             stdout=PIPE,
             stderr=PIPE,
@@ -89,43 +90,47 @@ class RemoteProcess(CommandProcess):
         self._process.wait()
 
         # Kill the remote program if possible
-        cmd = RemoteProcess.make_kill_script(self._pidfile)
+        cmd = ""
+        cmd += f"pid=$(cat {self._pidfile}); "
+        cmd += "if ps -p $pid >/dev/null; then "
+        cmd += "    kill $pid; "
+        cmd += "    echo 1; "
+        cmd += "else "
+        cmd += "    echo 0; "
+        cmd += "fi; "
+        cmd += f"rm {self._pidfile}"
         if not self._is_local:
-            cmd = f"ssh {self._host} {shlex.quote(cmd)}"
-        c = run(
-            cmd,
-            check=True,
-            shell=True,
-            executable="/bin/bash",
-            capture_output=True,
-            text=True,
-        )
+            cmd = f"ssh {self._host} '{cmd}'"
+        c = run(cmd, check=True, shell=True, capture_output=True, text=True)
 
         self._killed = c.stdout.strip() == "1"
 
     @staticmethod
-    def make_launch_script(rank, cwd, files, env, command):
+    def make_monitor_script(rank, cwd, files, env, command):
+        # Imports that are used throughout
         script = ""
-
-        # Disable echo
-        script = "stty -echo; "
+        script += "import os\n"
+        script += "import sys\n"
+        script += "import tempfile\n"
+        script += "from pathlib import Path\n"
 
         # Write the PID to a file so we can kill the process if needed
-        script += "pidfile=$(mktemp); "
-        script += "echo $$ > $pidfile; "
-        script += 'printf "%s\\n" $pidfile; '
+        script += "_, pidfile = tempfile.mkstemp() \n"
+        script += "open(pidfile, 'w').write(str(os.getpid()))\n"
+        script += "print(pidfile, flush=True)\n"
 
         # Change the working directory if one was requested. Otherwise attempt to
         # change to the current one but don't fail if it wasn't possible.
         d = cwd or os.getcwd()
-        script += f"if [[ -d {repr(d)} ]]; then "
-        script += f"  cd {repr(d)}; "
+        script += f"if Path({repr(d)}).exists():\n"
+        script += f"    os.chdir({repr(d)})\n"
         if cwd is not None:
-            script += "else "
-            script += f" echo 'Failed to change directory to' {repr(d)} >2; "
-        script += "fi; "
+            script += "else:\n"
+            script += f"    print('Failed to change directory to', {repr(d)}, file=sys.stderr)\n"
+            script += f"    sys.exit(1)\n"
 
         # Add the environment variables that were requested
+        script += "env = dict(os.environ)\n"
         for e in env:
             key, *value = e.split("=", maxsplit=1)
             value = shlex.quote(value[0]) if len(value) > 0 else ""
@@ -134,34 +139,22 @@ class RemoteProcess(CommandProcess):
                     f"'{e}' is an invalid environment variable so it is ignored"
                 )
                 continue
-            script += f"export {key}={value}; "
+            script += f"env[{repr(key)}] = {repr(value)}\n"
 
         # Make the temporary files
         for env_name, content in files.items():
-            script += "fname=$(mktemp); "
-            script += f"echo {shlex.quote(content)} >$fname; "
-            script += f"export {env_name}=$fname; "
+            script += "_, fname = tempfile.mkstemp()\n"
+            script += "with open(fname, 'w') as f:\n"
+            script += f"    f.write({repr(content)})\n"
+            script += f"env[{repr(env_name)}] = fname\n"
 
         # Finally add the rank
-        script += f"export MLX_RANK={rank}; "
+        script += f"env['MLX_RANK'] = '{rank}'\n"
+        script += "\n"
 
         # Replace the process with the script
-        script += f"cmd=({' '.join(map(shlex.quote, command))}); "
-        script += 'exec "${cmd[@]}"'
-
-        return script
-
-    @staticmethod
-    def make_kill_script(pidfile):
-        script = ""
-        script += f"pid=$(cat {pidfile}); "
-        script += "if ps -p $pid >/dev/null; then "
-        script += "    kill $pid; "
-        script += "    echo 1; "
-        script += "else "
-        script += "    echo 0; "
-        script += "fi; "
-        script += f"rm {pidfile}"
+        script += f"command = [{','.join(map(repr, command))}]\n"
+        script += "os.execve(command[0], command, env)\n"
 
         return script
 
@@ -316,7 +309,7 @@ def launch_ring(parser, hosts, args, command):
     _launch_with_io(
         RemoteProcess,
         [
-            ((rank, h.ssh_hostname, args.python, cwd, files, env, command), {})
+            ((rank, h.ssh_hostname, cwd, files, env, command), {})
             for rank, h in enumerate(hosts)
         ],
         args.verbose,
@@ -348,7 +341,6 @@ def launch_nccl(parser, hosts, args, command):
                 (
                     rank,
                     h.ssh_hostname,
-                    args.python,
                     cwd,
                     {},
                     env + [f"CUDA_VISIBLE_DEVICES={rank % args.repeat_hosts}"],
@@ -382,7 +374,7 @@ def launch_jaccl(parser, hosts, args, command):
     _launch_with_io(
         RemoteProcess,
         [
-            ((rank, h.ssh_hostname, args.python, cwd, files, env, command), {})
+            ((rank, h.ssh_hostname, cwd, files, env, command), {})
             for rank, h in enumerate(hosts)
         ],
         args.verbose,
@@ -511,20 +503,11 @@ def main():
         default=12345,
         help="The port to use for the NCCL communication (only for nccl backend)",
     )
-    parser.add_argument(
-        "--no-verify-script",
-        action="store_false",
-        dest="verify_script",
-        help="Do not verify that the script exists",
-    )
-    parser.add_argument(
-        "--python", default=sys.executable, help="Use this python on the remote hosts"
-    )
 
     args, rest = parser.parse_known_args()
 
     if args.print_python:
-        print(args.python)
+        print(sys.executable)
         return
 
     if len(rest) == 0:
@@ -540,10 +523,10 @@ def main():
 
     # Check if the script is a file and convert it to a full path
     if (script := Path(rest[0])).exists() and script.is_file():
-        rest[0:1] = [args.python, str(script.resolve())]
+        rest[0:1] = [sys.executable, str(script.resolve())]
     elif (command := shutil.which(rest[0])) is not None:
         rest[0] = command
-    elif args.verify_script:
+    else:
         raise ValueError(f"Invalid script or command {rest[0]}")
 
     # Launch

python/scripts/repair_cuda.sh

@@ -1,7 +1,7 @@
 #!/bin/bash
 
 auditwheel repair dist/* \
-  --plat manylinux_2_35_${1} \
+  --plat manylinux_2_35_x86_64 \
   --exclude libcublas* \
   --exclude libnvrtc* \
   --exclude libcuda* \

python/tests/test_reduce.py

@@ -210,14 +210,6 @@ class TestReduce(mlx_tests.MLXTestCase):
                     ref = getattr(np, op)(np_arr, axis=axis)
                     self.assertTrue(np.array_equal(out, ref, equal_nan=True))
 
-    def test_long_column(self):
-        a = (np.random.randn(8192, 64) * 32).astype(np.int32)
-        b = mx.array(a)
-
-        c1 = a.sum(0)
-        c2 = b.sum(0)
-        self.assertTrue(np.all(c1 == c2))
-
 
 if __name__ == "__main__":
     mlx_tests.MLXTestRunner(failfast=True)

setup.py

@@ -7,21 +7,13 @@ import re
 import subprocess
 from functools import partial
 from pathlib import Path
+from subprocess import run
 
 from setuptools import Command, Extension, find_namespace_packages, setup
 from setuptools.command.bdist_wheel import bdist_wheel
 from setuptools.command.build_ext import build_ext
 
 
-def cuda_toolkit_major_version():
-    out = subprocess.check_output(["nvcc", "--version"], stderr=subprocess.STDOUT)
-    text = out.decode()
-    m = re.search(r"release (\d+)", text)
-    if m:
-        return int(m.group(1))
-    return None
-
-
 def get_version():
     with open("mlx/version.h", "r") as fid:
         for l in fid:
@@ -39,7 +31,7 @@ def get_version():
         version = f"{version}.dev{today.year}{today.month:02d}{today.day:02d}"
     if not pypi_release and not dev_release:
         git_hash = (
-            subprocess.run(
+            run(
                 "git rev-parse --short HEAD".split(),
                 capture_output=True,
                 check=True,
@@ -266,7 +258,7 @@ if __name__ == "__main__":
     entry_points = {
         "console_scripts": [
             "mlx.launch = mlx._distributed_utils.launch:main",
-            "mlx.distributed_config = mlx._distributed_utils.config:main",
+            # "mlx.distributed_config = mlx.distributed_run:distributed_config",
         ]
     }
     install_requires = []
@@ -292,11 +284,7 @@ if __name__ == "__main__":
             install_requires.append(
                 f'mlx-metal=={version}; platform_system == "Darwin"'
             )
-            extras["cuda"] = [f'mlx-cuda-12=={version}; platform_system == "Linux"']
-            for toolkit in [12, 13]:
-                extras[f"cuda{toolkit}"] = [
-                    f'mlx-cuda-{toolkit}=={version}; platform_system == "Linux"'
-                ]
+            extras["cuda"] = [f'mlx-cuda=={version}; platform_system == "Linux"']
             extras["cpu"] = [f'mlx-cpu=={version}; platform_system == "Linux"']
 
         _setup(
@@ -311,25 +299,13 @@ if __name__ == "__main__":
         if build_macos:
             name = "mlx-metal"
         elif build_cuda:
-            toolkit = cuda_toolkit_major_version()
-            name = f"mlx-cuda-{toolkit}"
-            if toolkit == 12:
-                install_requires += [
-                    "nvidia-cublas-cu12==12.9.*",
-                    "nvidia-cuda-nvrtc-cu12==12.9.*",
-                ]
-            elif toolkit == 13:
-                install_requires += [
-                    "nvidia-cublas-cu13",
-                    "nvidia-cuda-nvrtc-cu13",
-                ]
-            else:
-                raise ValueError(f"Unknown toolkit {toolkit}")
+            name = "mlx-cuda"
             install_requires += [
-                f"nvidia-cudnn-cu{toolkit}==9.*",
-                f"nvidia-nccl-cu{toolkit}",
+                "nvidia-cublas-cu12==12.9.*",
+                "nvidia-cuda-nvrtc-cu12==12.9.*",
+                "nvidia-cudnn-cu12==9.*",
+                "nvidia-nccl-cu12",
             ]
-
         else:
             name = "mlx-cpu"
         _setup(

tests/array_tests.cpp

@@ -1,4 +1,5 @@
 // Copyright © 2023 Apple Inc.
+
 #include <climits>
 
 #include "doctest/doctest.h"
@@ -607,24 +608,3 @@ TEST_CASE("test make empty array") {
   CHECK_EQ(a.size(), 0);
   CHECK_EQ(a.dtype(), bool_);
 }
-
-TEST_CASE("test make array from user buffer") {
-  int size = 4096;
-  std::vector<int> buffer(size, 0);
-
-  int count = 0;
-  auto deleter = [&count](void*) { count++; };
-
-  {
-    auto a = array(buffer.data(), Shape{size}, int32, deleter);
-    if (metal::is_available()) {
-      CHECK_EQ(buffer.data(), a.data<int>());
-    }
-    auto b = a + array(1);
-    eval(b);
-    auto expected = ones({4096});
-    CHECK(array_equal(b, expected).item<bool>());
-  }
-  // deleter should always get called
-  CHECK_EQ(count, 1);
-}