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Get scalar from VRAM when using ROCm and large bar is enabled #3048

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Get scalar from VRAM when using ROCm and large bar is enabled #3048

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11 changes: 11 additions & 0 deletions aten/src/ATen/native/cuda/CUDAScalar.cu
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,14 @@ Scalar _local_scalar_dense_cuda(const Tensor& self) {
TORCH_CHECK(self.numel() > 0, "_local_scalar_dense: Empty tensor not supported");
AT_DISPATCH_V2(
self.scalar_type(), "_local_scalar_dense_cuda", AT_WRAP([&] {
#ifdef USE_ROCM
// If this is a large BAR device, we can just read directly from VRAM
if (at::cuda::getCurrentDeviceProperties()->isLargeBar) {
cudaStream_t stream = at::cuda::getCurrentCUDAStream();
at::cuda::stream_synchronize(stream);
r = Scalar(*self.const_data_ptr<scalar_t>());
} else {
#endif
// Create pinned memory for the scalar value to avoid implicit
// locking/sync in cuda library due to pageable memory
auto value = at::detail::empty_cpu(
Expand All @@ -31,6 +39,9 @@ Scalar _local_scalar_dense_cuda(const Tensor& self) {
cudaStream_t stream = at::cuda::getCurrentCUDAStream();
at::cuda::memcpy_and_sync(value.mutable_data_ptr<scalar_t>(), self.const_data_ptr<scalar_t>(), sizeof(scalar_t), cudaMemcpyDeviceToHost, stream);
r = Scalar(*value.const_data_ptr<scalar_t>());
#ifdef USE_ROCM
}
#endif
}), AT_EXPAND(AT_ALL_TYPES_AND_COMPLEX), kComplexHalf, kHalf, kBool, kBFloat16, AT_EXPAND(AT_FLOAT8_TYPES), AT_EXPAND(AT_BAREBONES_UNSIGNED_TYPES));
return r;
}
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