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mlx/mlx/backend/cuda/device/scatter.cuh
2025-06-12 21:44:19 -07:00

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// Copyright © 2025 Apple Inc.
#include "mlx/backend/cuda/device/indexing.cuh"
#include "mlx/backend/cuda/device/scatter_ops.cuh"
#include "mlx/backend/cuda/device/utils.cuh"
#include <cooperative_groups.h>
namespace mlx::core::cu {
namespace cg = cooperative_groups;
template <
typename T,
typename IdxT,
typename Op,
int NIDX,
int IDX_NDIM,
typename LocT>
__global__ void scatter(
const T* upd,
T* out,
LocT size,
const __grid_constant__ Shape upd_shape,
const __grid_constant__ Strides upd_strides,
int32_t upd_ndim,
LocT upd_post_idx_size,
const __grid_constant__ Shape out_shape,
const __grid_constant__ Strides out_strides,
int32_t out_ndim,
const __grid_constant__ cuda::std::array<int32_t, NIDX> axes,
const __grid_constant__ cuda::std::array<IdxT*, NIDX> indices,
const __grid_constant__ cuda::std::array<int32_t, NIDX * IDX_NDIM>
indices_shape,
const __grid_constant__ cuda::std::array<int64_t, NIDX * IDX_NDIM>
indices_strides) {
LocT upd_idx = cg::this_grid().thread_rank();
if (upd_idx >= size) {
return;
}
LocT out_elem = upd_idx % upd_post_idx_size;
LocT idx_elem = upd_idx / upd_post_idx_size;
LocT out_idx = elem_to_loc(
out_elem, upd_shape.data() + IDX_NDIM, out_strides.data(), out_ndim);
#pragma unroll
for (int i = 0; i < NIDX; ++i) {
LocT idx_loc = elem_to_loc_nd<IDX_NDIM>(
idx_elem,
indices_shape.data() + i * IDX_NDIM,
indices_strides.data() + i * IDX_NDIM);
int32_t axis = axes[i];
LocT idx_val = absolute_index(indices[i][idx_loc], out_shape[axis]);
out_idx += idx_val * out_strides[axis];
}
LocT upd_loc = elem_to_loc(
out_elem + idx_elem * upd_post_idx_size,
upd_shape.data(),
upd_strides.data(),
upd_ndim);
Op{}(out + out_idx, upd[upd_loc]);
}
} // namespace mlx::core::cu