Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

[release/2.4] [ROCm][layer_norm] Use __builtin_amdgcn_rcpf(x) instead of 1.f/x #1688

Open
wants to merge 1 commit into
base: release/2.4
Choose a base branch
from
+8 −0
Open

[release/2.4] [ROCm][layer_norm] Use __builtin_amdgcn_rcpf(x) instead of 1.f/x #1688

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
8 changes: 8 additions & 0 deletions aten/src/ATen/native/cuda/layer_norm_kernel.cu
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -126,7 +126,11 @@ WelfordDataLN cuWelfordOnlineSum(
{
U delta = val - curr_sum.mean;
U new_count = curr_sum.count + 1.f;
#ifdef USE_ROCM
U new_mean = curr_sum.mean + delta * __builtin_amdgcn_rcpf(new_count);
#else
U new_mean = curr_sum.mean + delta * (1.f/new_count); //proper division is slow, this is less accurate but noticeably faster
#endif
return {new_mean, curr_sum.sigma2 + delta * (val - new_mean), new_count};
}

Expand All @@ -140,7 +144,11 @@ WelfordDataLN cuWelfordCombine(
U count = dataA.count + dataB.count;
U mean, sigma2;
if (count > decltype(dataB.count){0}) {
#ifdef USE_ROCM
auto coef = __builtin_amdgcn_rcpf(count);
#else
auto coef = 1.f/count; //NB we don't use --use_fast_math, but this is emulation, 1./count goes to intrinsic, `* coef` is multiplication, instead of slow fp division
#endif
auto nA = dataA.count * coef;
auto nB = dataB.count * coef;
mean = nA*dataA.mean + nB*dataB.mean;
Expand Down