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mlx/mlx/backend/cuda/ternary.cu
2025-10-31 14:12:15 -07:00

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// Copyright © 2025 Apple Inc.
#include "mlx/backend/common/ternary.h"
#include "mlx/backend/cuda/device.h"
#include "mlx/backend/cuda/device/ternary_ops.cuh"
#include "mlx/backend/cuda/kernel_utils.cuh"
#include "mlx/dtype_utils.h"
#include "mlx/primitives.h"
#include <cooperative_groups.h>
#include <nvtx3/nvtx3.hpp>
namespace mlx::core {
namespace cu {
namespace cg = cooperative_groups;
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 + 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[i] = Op{}(a_vec[i], b_vec[i], c_vec[i]);
}
store_vector<N_READS>(out, index, out_vec);
}
}
template <typename Op, typename T, typename IdxT, int NDIM, int N_READS>
__global__ void ternary_g_nd(
const bool* a,
const T* b,
const T* c,
T* out,
IdxT size_rest,
const __grid_constant__ cuda::std::array<int32_t, NDIM> shape,
const __grid_constant__ cuda::std::array<int64_t, NDIM> a_strides,
const __grid_constant__ cuda::std::array<int64_t, NDIM> b_strides,
const __grid_constant__ cuda::std::array<int64_t, NDIM> c_strides) {
auto block = cg::this_thread_block();
auto grid = cg::this_grid();
IdxT index_rest =
grid.block_index().y * block.dim_threads().y + block.thread_index().y;
if (index_rest >= size_rest) {
return;
}
auto shape_x = shape[NDIM - 1];
auto a_stride_x = a_strides[NDIM - 1];
auto b_stride_x = b_strides[NDIM - 1];
auto c_stride_x = c_strides[NDIM - 1];
IdxT index_x =
grid.block_index().x * block.dim_threads().x + block.thread_index().x;
auto [a_idx, b_idx, c_idx] = elem_to_loc_nd<NDIM>(
index_rest * shape_x,
shape.data(),
a_strides.data(),
b_strides.data(),
c_strides.data());
auto a_vec =
load_vector<N_READS>(a + a_idx, index_x, shape_x, a_stride_x, false);
auto b_vec =
load_vector<N_READS>(b + b_idx, index_x, shape_x, b_stride_x, T(0));
auto c_vec =
load_vector<N_READS>(c + c_idx, index_x, shape_x, c_stride_x, T(0));
AlignedVector<T, N_READS> out_vec;
#pragma unroll
for (int i = 0; i < N_READS; ++i) {
out_vec[i] = Op{}(a_vec[i], b_vec[i], c_vec[i]);
}
store_vector(out + shape_x * index_rest, index_x, out_vec, shape_x);
}
template <typename Op, typename T, typename IdxT, int N_READS>
__global__ void ternary_g(
const bool* a,
const T* b,
const T* c,
T* out,
IdxT size_rest,
const __grid_constant__ Shape shape,
const __grid_constant__ Strides a_strides,
const __grid_constant__ Strides b_strides,
const __grid_constant__ Strides c_strides,
int ndim) {
auto block = cg::this_thread_block();
auto grid = cg::this_grid();
IdxT index_rest =
grid.block_index().y * block.dim_threads().y + block.thread_index().y;
if (index_rest >= size_rest) {
return;
}
auto shape_x = shape[ndim - 1];
auto a_stride_x = a_strides[ndim - 1];
auto b_stride_x = b_strides[ndim - 1];
auto c_stride_x = c_strides[ndim - 1];
IdxT index_x =
grid.block_index().x * block.dim_threads().x + block.thread_index().x;
auto [a_idx, b_idx, c_idx] = elem_to_loc(
index_rest * shape_x,
shape.data(),
a_strides.data(),
b_strides.data(),
c_strides.data(),
ndim);
auto a_vec =
load_vector<N_READS>(a + a_idx, index_x, shape_x, a_stride_x, false);
auto b_vec =
load_vector<N_READS>(b + b_idx, index_x, shape_x, b_stride_x, T(0));
auto c_vec =
load_vector<N_READS>(c + c_idx, index_x, shape_x, c_stride_x, T(0));
AlignedVector<T, N_READS> out_vec;
#pragma unroll
for (int i = 0; i < N_READS; ++i) {
out_vec[i] = Op{}(a_vec[i], b_vec[i], c_vec[i]);
}
store_vector(out + shape_x * index_rest, index_x, out_vec, shape_x);
}
} // namespace cu
template <typename Op>
void ternary_op_gpu_inplace(
const std::vector<array>& inputs,
array& out,
const Stream& s) {
const auto& a = inputs[0];
const auto& b = inputs[1];
const auto& c = inputs[2];
if (out.size() == 0) {
return;
}
auto& encoder = cu::get_command_encoder(s);
encoder.set_input_array(a);
encoder.set_input_array(b);
encoder.set_input_array(c);
encoder.set_output_array(out);
dispatch_all_types(out.dtype(), [&](auto type_tag) {
using DType = cuda_type_t<MLX_GET_TYPE(type_tag)>;
auto topt = get_ternary_op_type(a, b, c);
if (topt == TernaryOpType::VectorVectorVector ||
topt == TernaryOpType::ScalarScalarScalar) {
dispatch_bool(out.data_size() > UINT32_MAX, [&](auto large) {
using IdxT = std::conditional_t<large(), int64_t, uint32_t>;
constexpr int N_READS = 16 / sizeof(DType);
auto [num_blocks, block_dims] = get_launch_args(
out.data_size(), out.shape(), out.strides(), large(), N_READS);
encoder.add_kernel_node(
cu::ternary_v<Op, DType, IdxT, N_READS>,
num_blocks,
block_dims,
0,
gpu_ptr<bool>(a),
gpu_ptr<DType>(b),
gpu_ptr<DType>(c),
gpu_ptr<DType>(out),
out.data_size());
});
} else {
dispatch_bool(
a.data_size() > INT32_MAX || b.data_size() > INT32_MAX ||
c.data_size() > INT32_MAX || out.data_size() > INT32_MAX,
[&](auto large) {
using IdxT = std::conditional_t<large(), int64_t, int32_t>;
Shape shape;
std::vector<Strides> strides;
std::tie(shape, strides) = collapse_contiguous_dims(a, b, c, out);
auto& a_strides = strides[0];
auto& b_strides = strides[1];
auto& c_strides = strides[2];
int ndim = shape.size();
int work_per_thread = 1;
auto dim0 = ndim > 0 ? shape.back() : 1;
auto rest = out.size() / dim0;
if (dim0 >= 4) {
work_per_thread = 4;
}
dim0 = (dim0 + work_per_thread - 1) / work_per_thread;
auto block_dims = get_block_dims(dim0, rest, 1);
uint32_t num_blocks_x = cuda::ceil_div(dim0, block_dims.x);
uint32_t num_blocks_y = cuda::ceil_div(rest, block_dims.y);
if (ndim <= 3) {
dispatch_1_2_3(ndim, [&](auto dims_constant) {
auto kernel =
cu::ternary_g_nd<Op, DType, IdxT, dims_constant(), 1>;
if (work_per_thread == 4) {
kernel =
cu::ternary_g_nd<Op, DType, IdxT, dims_constant(), 4>;
}
encoder.add_kernel_node(
kernel,
{num_blocks_x, num_blocks_y},
block_dims,
0,
gpu_ptr<bool>(a),
gpu_ptr<DType>(b),
gpu_ptr<DType>(c),
gpu_ptr<DType>(out),
rest,
const_param<dims_constant()>(shape),
const_param<dims_constant()>(a_strides),
const_param<dims_constant()>(b_strides),
const_param<dims_constant()>(c_strides));
});
} else {
auto kernel = cu::ternary_g<Op, DType, IdxT, 1>;
if (work_per_thread == 4) {
kernel = cu::ternary_g<Op, DType, IdxT, 4>;
}
encoder.add_kernel_node(
kernel,
{num_blocks_x, num_blocks_y},
block_dims,
0,
gpu_ptr<bool>(a),
gpu_ptr<DType>(b),
gpu_ptr<DType>(c),
gpu_ptr<DType>(out),
rest,
const_param(shape),
const_param(a_strides),
const_param(b_strides),
const_param(c_strides),
ndim);
}
});
}
});
}
template <typename Op>
void ternary_op_gpu(
const std::vector<array>& inputs,
array& out,
const Stream& s) {
auto& a = inputs[0];
auto& b = inputs[1];
auto& c = inputs[2];
auto topt = get_ternary_op_type(a, b, c);
auto& encoder = cu::get_command_encoder(s);
set_ternary_op_output_data(a, b, c, out, topt, [&](auto n) {
return cu::malloc_async(n, encoder.stream());
});
ternary_op_gpu_inplace<Op>(inputs, out, s);
}
void Select::eval_gpu(const std::vector<array>& inputs, array& out) {
nvtx3::scoped_range r("Select::eval_gpu");
auto& s = out.primitive().stream();
ternary_op_gpu<cu::Select>(inputs, out, s);
}
} // namespace mlx::core