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[Bugfix] Fix nll bug via decomposition handling#177189

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[Bugfix] Fix nll bug via decomposition handling#177189
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@Lucaskabela Lucaskabela commented Mar 11, 2026 •
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Fixes #89630

Summary

NLL backward was failing under compile with 1d input when self is 1D, where target.unsqueeze(0) produced
a 2D index for the subsequent 1D scatter. The fix mirrors the C++ kernel's behavior of only using
target[0]

Test

python -m pytest test/inductor/test_torchinductor.py -xvs -k "test_nll_loss_backward_1d_input"

cc @voznesenskym @penguinwu @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @ipiszy @kadeng @muchulee8 @amjames @chauhang @aakhundov @coconutruben @jataylo

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pytorch-bot bot commented Mar 11, 2026 •
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🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/177189

Note: Links to docs will display an error until the docs builds have been completed.

❌ 1 New Failure, 2 Unrelated Failures

As of commit 9ae0c7d with merge base f249065 (image):

NEW FAILURE - The following job has failed:

FLAKY - The following job failed but was likely due to flakiness present on trunk:

UNSTABLE - The following job is marked as unstable, possibly due to flakiness on trunk:

This comment was automatically generated by Dr. CI and updates every 15 minutes.

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pytorch-bot bot commented Mar 11, 2026

This PR needs a release notes: label

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@Lucaskabela Lucaskabela force-pushed the lucaskabela/nll_bugfix branch from b968311 to 9ae0c7d Compare March 11, 2026 21:40
@Lucaskabela Lucaskabela marked this pull request as ready for review March 11, 2026 21:40
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Lucaskabela commented Mar 11, 2026

@claude are these test failures related to my change?

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claude bot commented Mar 11, 2026 •
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Claude finished @Lucaskabela's task in 1m 13s —— View job

CI Failure Analysis

  • Review the PR changes to understand scope
  • Analyze each CI failure for relevance to the change
  • Provide summary

No, none of the CI failures are related to your change. Here's the breakdown:

1. linux-jammy-py3.14-clang15 / test (crossref, 1, 2) — Not related

This job was killed with exit code 137 (SIGKILL), which is the OOM killer. The logs show it was running test_fx.py when the process was killed — a test file completely unrelated to NLL loss or decompositions. This is a resource/memory issue on the CI runner, not a test failure caused by your code.

2. test_dtensor_op_db_nanmean_cpu_float32 — Not related (flaky)

Already marked as flaky by the CI bot, with a similar failure on trunk. This is a distributed tensor test unrelated to NLL loss.

3. detectron2_maskrcnn_r_50_fpn — Not related (unstable)

Marked as unstable and linked to existing issue #174929. This is an inductor benchmark flake, not related to your change.

Your change only touches torch/_decomp/decompositions.py (6 lines) and adds a test in test/inductor/test_torchinductor.py. None of the failures involve these files or the NLL loss code path.

@Lucaskabela Lucaskabela requested a review from azahed98 March 12, 2026 00:16
frgossen
frgossen reviewed Mar 12, 2026
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@Lucaskabela Lucaskabela requested a review from frgossen March 12, 2026 15:58
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Lucaskabela commented Mar 12, 2026

@pytorchbot merge

@pytorch-bot pytorch-bot bot added the ciflow/trunk Trigger trunk jobs on your pull request label Mar 12, 2026
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pytorchmergebot commented Mar 12, 2026

Merge failed

Reason: This PR needs a release notes: label
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If not, please add the topic: not user facing label.

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Details for Dev Infra team Raised by workflow job

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This PR needs a release notes: label

If your changes are user facing and intended to be a part of release notes, please use a label starting with release notes:.

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Lucaskabela commented Mar 12, 2026

@pytorchbot label "topic: not user facing"

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Lucaskabela commented Mar 12, 2026

@pytorchbot merge -i

@pytorch-bot pytorch-bot bot added the topic: not user facing topic category label Mar 12, 2026
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pytorchmergebot commented Mar 12, 2026

Merge started

Your change will be merged while ignoring the following 3 checks: pull / linux-jammy-py3.14-clang15 / test (crossref, 1, 2, lf.linux.2xlarge), pull / linux-jammy-py3.10-gcc11 / test (distributed, 1, 2, lf.linux.2xlarge), inductor / inductor-cpu-test / test (cpu_inductor_torchbench, 1, 2, linux.2xlarge.amx, unstable)

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EmanueleCoradin pushed a commit to EmanueleCoradin/pytorch that referenced this pull request Mar 30, 2026
@Lucaskabela @EmanueleCoradin
[Bugfix] Fix nll bug via decomposition handling (pytorch#177189)
10d45a9 
Fixes pytorch#89630

## Summary
NLL backward was failing under compile with 1d input when self is 1D, where target.unsqueeze(0) produced
  a 2D index for the subsequent 1D scatter. The fix mirrors the C++ kernel's behavior of only using
  target[0]

## Test
```bash
python -m pytest test/inductor/test_torchinductor.py -xvs -k "test_nll_loss_backward_1d_input"
```

Pull Request resolved: pytorch#177189
Approved by: https://github.com/frgossen
@github-actions github-actions bot deleted the lucaskabela/nll_bugfix branch April 12, 2026 02:25
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[dynamo] RuntimeError: Failed running call_function aten.nll_loss_backward(*(FakeTensor(FakeTensor(...

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