Fix a bug of distributed 'gather' with noncontiguous tensors on the NCCL backend. #159549
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🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/159549
Note: Links to docs will display an error until the docs builds have been completed. ⏳ 1 Pending, 1 Unrelated FailureAs of commit 829e141 with merge base 42a69f7 ( UNSTABLE - The following job is marked as unstable, possibly due to flakiness on trunk:
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d4l3k
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Jul 31, 2025
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@pytorchbot merge |
Merge startedYour change will be merged once all checks pass (ETA 0-4 Hours). Learn more about merging in the wiki. Questions? Feedback? Please reach out to the PyTorch DevX Team |
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I would be glad to add some unit tests for the bug, but I am not familiar with the testing framework and do not know where to start. :( |
yangw-dev
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Aug 1, 2025
…CCL backend. (#159549) Fixes #159548 * Throw an error message when the input tensors for the distributed `gather` are noncontiguous. This behaviour is consistent with the distributed `all_gather`. Pull Request resolved: #159549 Approved by: https://github.com/d4l3k
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cc @zhangxiaoli73 @Chao1Han I think the xccl backend needs this fix as well... |
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@Chao1Han Please help check.
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Fixes #159548
gatherare noncontiguous. This behaviour is consistent with the distributedall_gather.cc @H-Huang @awgu @wanchaol @fegin @fduwjj @wz337 @wconstab @d4l3k @pragupta