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Schedule remainder loop chunk in threadblock 0. #1985

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Schedule remainder loop chunk in threadblock 0. #1985

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17 changes: 11 additions & 6 deletions aten/src/ATen/native/cuda/CUDALoops.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -182,8 +182,12 @@ __global__ void vectorized_templated_elementwise_kernel(
loader_t loader,
storer_t storer) {
using traits = function_traits<func_t>;
// Remainder chunk uses slower scheme than vectorized:
// assign it in the first threadblock to enable scheduler
// to start is as soon as possible, by inverting mapping
// of loop chunks to threadblocks.
int remaining =
N - vectorized_templated_config::block_work_size() * blockIdx.x;
N - vectorized_templated_config::block_work_size() * (gridDim.x - blockIdx.x - 1);
if (remaining <
vectorized_templated_config::block_work_size()) { // if this block handles
// the reminder,
Expand All @@ -197,20 +201,21 @@ __global__ void vectorized_templated_elementwise_kernel(
out_calc_t,
loader_t,
storer_t>(data, remaining, inp_calc, out_calc, loader, storer);
templated_elementwise_kernel_helper(f, policy);
templated_elementwise_kernel_helper</*reverted_idx=*/true>(f, policy);
} else { // if this block has a full `block_work_size` data to handle, use
// vectorized memory access
templated_elementwise_kernel_helper<
vectorized_templated_config::thread_work_size()>(
f,
auto policy =
memory::policies::vectorized_templated<
vectorized_templated_config::thread_work_size(),
vectorized_templated_config::num_threads(),
vectorized_templated_config::block_work_size(),
vec_size,
array_t,
OutputType,
InputTypes...>(data));
InputTypes...>(data);
templated_elementwise_kernel_helper</*reverted_idx=*/true,
vectorized_templated_config::thread_work_size()>(
f, policy);
}
}

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3 changes: 3 additions & 0 deletions aten/src/ATen/native/cuda/Loops.cuh
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,7 @@ __device__ inline void elementwise_kernel_helper(func_t f, policy_t policy) {

#ifdef USE_ROCM
template <
bool reverted_idx=false,
int thread_work_size = thread_work_size(),
typename func_t,
typename policy_t>
Expand All @@ -79,6 +80,8 @@ __device__ inline void templated_elementwise_kernel_helper(
using args_t = typename traits::ArgsTuple;

int idx = blockIdx.x;
if constexpr (reverted_idx)
idx = gridDim.x - blockIdx.x - 1;

return_t results[thread_work_size];
args_t args[thread_work_size];
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