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[AUTOGENERATED] [release/2.6] [ROCm] Enable more parallelism for multi-dimensional reductions #2297

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Jun 27, 2025
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[AUTOGENERATED] [release/2.6] [ROCm] Enable more parallelism for multi-dimensional reductions #2297

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20 changes: 13 additions & 7 deletions aten/src/ATen/native/cuda/Reduce.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -1115,13 +1115,19 @@ ReduceConfig setReduceConfig(const TensorIterator& iter){
int max_threads_per_mp =
at::cuda::getCurrentDeviceProperties()->maxThreadsPerMultiProcessor;
#ifdef USE_ROCM
// Control the number of threadblocks by adjusting the maximum number of
// threads per multi-processor. These numbers better reflect the maximum
// theoretical achievable threads per MP for the reduction operation.
if (iter.ndim() == 1 || iter.ndim() == 3)
max_threads_per_mp = 512;
if (iter.ndim() == 2)
max_threads_per_mp = 256;
// If the grid consists of a single threadblock, do not change the max threads per
// MP value. This will increase the parallelism across the y dimension of the grid.
bool uses_a_single_block = config.grid().x == config.grid().y == config.grid().z == 1;

if (!uses_a_single_block) {
// Control the number of threadblocks by adjusting the maximum number of
// threads per multi-processor. These numbers better reflect the maximum
// theoretical achievable threads per MP for the reduction operation.
if (iter.ndim() == 1 || iter.ndim() == 3)
max_threads_per_mp = 512;
else if (iter.ndim() == 2)
max_threads_per_mp = 256;
}
#endif
const int blocks_per_sm = max_threads_per_mp / config.num_threads;
const int target_grid_size = num_mp * blocks_per_sm;
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