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FIX avoid torch dlpack crash for negative strides - #34380

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virchan merged 3 commits into
scikit-learn:mainfrom
yinli-systems:codex/fix-torch-negative-strides-dlpack
Jul 9, 2026
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FIX avoid torch dlpack crash for negative strides#34380
virchan merged 3 commits into
scikit-learn:mainfrom
yinli-systems:codex/fix-torch-negative-strides-dlpack

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@yinli-systems

@yinli-systems yinli-systems commented Jun 24, 2026

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Reference Issues/PRs

Fixes #34307.
Related to pytorch/pytorch#188023.

What does this implement/fix? Explain your changes.

move_to currently transfers NumPy arrays to torch through DLPack when possible. PyTorch aborts the Python process when importing a NumPy array with negative strides through DLPack, before scikit-learn can fall back to a safer conversion path.

This adds a narrow workaround for the affected path: when the source array is NumPy, the target namespace is torch, and any stride is negative, move_to first makes the array contiguous with numpy.ascontiguousarray before calling xp.from_dlpack. Other namespaces and non-negative-strided NumPy arrays continue to use the existing path.

The regression test runs in a subprocess because the previous failure mode aborts the Python process instead of raising a Python exception.

Any other comments?

Validation run locally:

MPLCONFIGDIR=/private/tmp/mplconfig LOKY_MAX_CPU_COUNT=8 PATH="$PWD/.venv/bin:$PATH" .venv/bin/python -m pytest sklearn/utils/tests/test_array_api.py::test_move_to_numpy_negative_strides_to_torch sklearn/utils/tests/test_array_api.py::test_move_to_array_api_conversions sklearn/utils/tests/test_array_api.py::test_move_to_sparse -q

Result: 1 passed, 6 skipped.

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@yinli-systems

yinli-systems commented Jun 28, 2026

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Status note: all test/lint/docs/codecov checks are passing. The only red check is the repository changelog gate ("A reviewer will let you know if it is required or can be bypassed"), so I am leaving it for reviewer guidance rather than adding a changelog entry preemptively.

@yinli-systems
yinli-systems force-pushed the codex/fix-torch-negative-strides-dlpack branch from 579c68b to 197081f Compare June 28, 2026 10:59
ogrisel
ogrisel reviewed Jul 1, 2026
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The change LGTM besides the following detail.

Comment thread sklearn/utils/_array_api.py Outdated
@ogrisel ogrisel added the CUDA CI label Jul 1, 2026
@github-actions github-actions Bot removed the CUDA CI label Jul 1, 2026
@ogrisel ogrisel moved this to In Progress in Array API Jul 1, 2026
@ogrisel

ogrisel commented Jul 1, 2026

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Also, please disclose AI usage when making PRs as requested in the PR template.

@yinli-systems

yinli-systems commented Jul 1, 2026 •
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Thanks, addressed in the latest push. The negative-stride workaround now uses nested conditions so that array.strides is only accessed after confirming the source namespace is NumPy.

Local validation:

  • git diff --check
  • PYTHONPYCACHEPREFIX=/private/tmp/sklearn-pr34380-pycache /usr/bin/python3 -m py_compile sklearn/utils/_array_api.py sklearn/utils/tests/test_array_api.py

I also attempted the targeted pytest in the temporary checkout, but this fresh clone has not been built with Meson, so pytest stops at the expected sklearn.__check_build._check_build import error before collecting the test.

Also, to disclose AI usage as requested in the PR template: I used AI assistance while preparing this PR, mainly to help reason about the edge case and organize/check local validation. I reviewed the final code changes and validation output myself before submitting.

ogrisel
ogrisel approved these changes Jul 8, 2026
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LGTM. Any second review @betatim @virchan @OmarManzoor?

Comment thread doc/whats_new/upcoming_changes/sklearn.utils/34380.fix.rst Outdated
@virchan @ogrisel
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3a42fdc 
Co-authored-by: Olivier Grisel <[email protected]>
virchan
virchan approved these changes Jul 9, 2026
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LGTM! Thanks, @Kevin-Li-2025!

I applied #34380 (comment) directly, and enabled auto-merge.

@virchan
virchan enabled auto-merge (squash) July 9, 2026 07:54
@virchan
virchan merged commit f801a5e into scikit-learn:main Jul 9, 2026
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@github-project-automation github-project-automation Bot moved this from In Progress to Done in Array API Jul 9, 2026
@betatim

betatim commented Jul 9, 2026

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I don't know why the "check job statuses" job was cancelled, I restarted it and it succeeded

@yinli-systems
yinli-systems deleted the codex/fix-torch-negative-strides-dlpack branch August 29, 2026 09:17
prady0t pushed a commit to prady0t/scikit-learn that referenced this pull request Sep 2, 2026
@yinli-systems Kevin-Li-2025
@virchan @ogrisel @prady0t
FIX avoid torch dlpack crash for negative strides (scikit-learn#34380)
fe1d7d9 
Co-authored-by: Kevin-Li-2025 <[email protected]>
Co-authored-by: Virgil Chan <[email protected]>
Co-authored-by: Olivier Grisel <[email protected]>
@jeremiedbb jeremiedbb mentioned this pull request Sep 8, 2026
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jeremiedbb pushed a commit to jeremiedbb/scikit-learn that referenced this pull request Sep 9, 2026
@yinli-systems Kevin-Li-2025
@virchan @ogrisel @jeremiedbb
FIX avoid torch dlpack crash for negative strides (scikit-learn#34380)
76fb18f 
Co-authored-by: Kevin-Li-2025 <[email protected]>
Co-authored-by: Virgil Chan <[email protected]>
Co-authored-by: Olivier Grisel <[email protected]>
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Using move_to on a numpy array with negative stride crashes the Python process

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