[ExecuTorch][WebGPU] Add argmax/argmin ops + int64-output path#21209
Open
JCNTH wants to merge 1 commit into
Open
[ExecuTorch][WebGPU] Add argmax/argmin ops + int64-output path#21209JCNTH wants to merge 1 commit into
JCNTH wants to merge 1 commit into
Conversation
🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/21209
Note: Links to docs will display an error until the docs builds have been completed. ❗ 1 Active SEVsThere are 1 currently active SEVs. If your PR is affected, please view them below: ❌ 46 New Failures, 3 Unrelated FailuresAs of commit feb7511 with merge base 266e0dc ( NEW FAILURES - The following jobs have failed:
FLAKY - The following jobs failed but were likely due to flakiness present on trunk:
BROKEN TRUNK - The following job failed but were present on the merge base:👉 Rebase onto the `viable/strict` branch to avoid these failures
This comment was automatically generated by Dr. CI and updates every 15 minutes. |
This was referenced Jul 22, 2026
This was referenced Jul 22, 2026
This PR needs a
|
meta-cla
Bot
added
the
CLA Signed
psiddh
approved these changes
Jul 23, 2026
psiddh
left a comment
psiddh
left a comment
Contributor
There was a problem hiding this comment.
Approving full WebGPU stack
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Stack from ghstack (oldest at bottom):
Problem: The WebGPU delegate has no
aten.argmax.default/aten.argmin.default, and — more fundamentally — no int64-OUTPUT support: the AOT downcasts the int64 index to an int32 GPU buffer, but the ExecuTorch program output is int64, andcopy_outputsraw-copied the int64 EValue's bytes from the int32 staging buffer (a size mismatch). argmax would be the first int64-output op. argmax unlocks on-GPU decode sampling.Solution: Port
et_vk.argmax/argmin(last-dim arg-reduction -> int64 index) sharing one handler, mirroring VulkanArgReduce.cpp(arg_reduce_impl, last-dim only, theadd_reduce_per_row_nodeaccumulator that tracks{val, idx}). The kernel reuses the landedamaxlast-dim reduction + index-tracking: a strict>(argmax) /<(argmin) scan keeps the FIRST extremum (= torch tie-break), writing the index as int32 (1 u32/row) to the int32 GPU buffer. Add the int32->int64 output-widening path:copy_outputsnow maps each output's LIVE staging size (cur_nbytes) and, when the host EValue is 2x the int staging buffer, sign-extends int32->int64 into the EValue; matched-dtype outputs keep the unchanged raw-copy path.Implementation:
argmax/Reduce.cppregistersaten.argmax.default+aten.argmin.default->arg_reduce_impl(graph, args, is_argmin); args[in, dim, keepdim, out],dimscalar (last-dim guard),out = args.back(), guards fp32 input / int32 output / shape, resize hook.arg_reduce.wgslis one row per thread.WebGPUGraph::copy_outputsmapscur_nbytes+ the guardeddst == 2*map && is_intwiden.WebGPUBackend::executewrapsexecute()+copy_outputs()in try/catch so a defensive throw never crosses the backend boundary.Constraints: last-dim reduction only (mirrors Vulkan
normalized_dim == ndim-1); fp32 input, int32-backed int64 index output. Thecopy_outputschange is byte-identical for every existing fp32/int8 output (cur_nbytes == EValue nbytesfor matched dtypes) — verified by regression (floor_divide fp32, q8ta convs int8 all still pass).Differential Revision: D112257656