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Add option to FakeProcessGroup to raise error if comms are invoked.#162841

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Add option to FakeProcessGroup to raise error if comms are invoked.#162841
ezyang wants to merge 3 commits intogh/ezyang/3151/basefrom
gh/ezyang/3151/head

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@ezyang ezyang commented Sep 12, 2025

Stack from ghstack (oldest at bottom):

The current behavior is to do "nothing", which means you will corrupt
data. If you're doing something similar to LocalTensor, where you're
overriding the behavior of collectives to do something numerically,
this can be unwelcome behavior. If you can error when this happens
it can help prevent silent numerical incorrectness.

Authored with claude code.

Signed-off-by: Edward Yang ezyang@meta.com

cc @H-Huang @awgu @wanchaol @fegin @fduwjj @wz337 @wconstab @d4l3k @pragupta @msaroufim @dcci

[ghstack-poisoned]
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pytorch-bot bot commented Sep 12, 2025

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/162841

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

❌ 1 New Failure

As of commit 36f0bab with merge base d633bac (image):

NEW FAILURE - The following job has failed:

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ezyang added a commit that referenced this pull request Sep 12, 2025
The current behavior is to do "nothing", which means you will corrupt
data.  If you're doing something similar to LocalTensor, where you're
overriding the behavior of collectives to do something numerically,
this can be unwelcome behavior.  If you can error when this happens
it can help prevent silent numerical incorrectness.

Authored with claude code.

Signed-off-by: Edward Yang <ezyang@meta.com>
ghstack-source-id: 9dff853
Pull-Request: #162841
@pytorch-bot pytorch-bot bot added oncall: distributed Add this issue/PR to distributed oncall triage queue release notes: distributed (c10d) release notes category labels Sep 12, 2025
@albanD albanD removed their request for review September 12, 2025 20:09
[ghstack-poisoned]
ezyang added a commit that referenced this pull request Sep 29, 2025
The current behavior is to do "nothing", which means you will corrupt
data.  If you're doing something similar to LocalTensor, where you're
overriding the behavior of collectives to do something numerically,
this can be unwelcome behavior.  If you can error when this happens
it can help prevent silent numerical incorrectness.

Authored with claude code.

Signed-off-by: Edward Yang <ezyang@meta.com>
ghstack-source-id: 3d4910b
Pull-Request: #162841
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ezyang commented Sep 29, 2025

@pytorchbot merge

@pytorch-bot pytorch-bot bot added the ciflow/trunk Trigger trunk jobs on your pull request label Sep 29, 2025
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Merge started

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Merge failed

Reason: 1 mandatory check(s) failed. The first few are:

Dig deeper by viewing the failures on hud

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Failing merge rule: Core Maintainers

[ghstack-poisoned]
ezyang added a commit that referenced this pull request Sep 29, 2025
The current behavior is to do "nothing", which means you will corrupt
data.  If you're doing something similar to LocalTensor, where you're
overriding the behavior of collectives to do something numerically,
this can be unwelcome behavior.  If you can error when this happens
it can help prevent silent numerical incorrectness.

Authored with claude code.

Signed-off-by: Edward Yang <ezyang@meta.com>
ghstack-source-id: 98cddeb
Pull-Request: #162841
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ezyang commented Sep 29, 2025

@pytorchbot merge

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Merge started

Your 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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Merge failed

Reason: 1 jobs have failed, first few of them are: trunk / linux-jammy-rocm-py3.10 / test (distributed, 1, 1, linux.rocm.gpu.gfx942.4)

Details for Dev Infra team Raised by workflow job

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ezyang commented Oct 1, 2025

@pytorchbot merge -i

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Merge started

Your change will be merged while ignoring the following 1 checks: trunk / linux-jammy-rocm-py3.10 / test (distributed, 1, 1, linux.rocm.gpu.gfx942.4)

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Questions? Feedback? Please reach out to the PyTorch DevX Team

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Chao1Han pushed a commit to Chao1Han/pytorch that referenced this pull request Oct 21, 2025
…ytorch#162841)

The current behavior is to do "nothing", which means you will corrupt
data.  If you're doing something similar to LocalTensor, where you're
overriding the behavior of collectives to do something numerically,
this can be unwelcome behavior.  If you can error when this happens
it can help prevent silent numerical incorrectness.

Authored with claude code.

Signed-off-by: Edward Yang <ezyang@meta.com>

Pull Request resolved: pytorch#162841
Approved by: https://github.com/dcci
@github-actions github-actions bot deleted the gh/ezyang/3151/head branch November 1, 2025 02:20
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