mlx/mlx/backend/cuda/reduce/init_reduce.cu
2025-07-01 01:33:44 -07:00

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// Copyright © 2025 Apple Inc.
#include "mlx/backend/cuda/device.h"
#include "mlx/backend/cuda/reduce/reduce.cuh"
#include <cooperative_groups.h>
namespace mlx::core {
namespace cu {
namespace cg = cooperative_groups;
template <typename T, typename U, typename Op>
__global__ void init_reduce(U* out, size_t size) {
auto index = cg::this_grid().thread_rank();
if (index < size) {
out[index] = ReduceInit<Op, T>::value();
}
}
} // namespace cu
void init_reduce(
cu::CommandEncoder& encoder,
const array& in,
array& out,
Reduce::ReduceType reduce_type) {
// Allocate if needed
if (out.data_shared_ptr() == nullptr) {
out.set_data(allocator::malloc(out.nbytes()));
}
encoder.set_output_array(out);
encoder.launch_kernel([&](cudaStream_t stream) {
dispatch_all_types(in.dtype(), [&](auto type_tag) {
dispatch_reduce_ops(reduce_type, [&](auto reduce_type_tag) {
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;
auto kernel = cu::init_reduce<T, U, OP>;
dim3 grid = get_2d_grid_dims(out.shape(), out.strides());
dim3 block(grid.x < 1024 ? grid.x : 1024, 1, 1);
grid.x = (grid.x + 1023) / 1024;
kernel<<<grid, block, 0, stream>>>(out.data<U>(), out.size());
});
});
});
}
} // namespace mlx::core