Fix FT allreduce bug #1170
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Fix FT allreduce bug #1170
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fegin
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May 6, 2025
| @@ -59,7 +58,7 @@ def get_dp_info(self, dp_degree: int, dp_rank: int) -> tuple[int, int]: | |||
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| def set_all_reduce_hook(self, model_parts: list[torch.nn.Module]) -> None: | |||
| def all_reduce_hook(output): | |||
| dist.all_reduce(output, group=self.replicate_pg, op=ReduceOp.AVG) | |||
| self.replicate_pg.allreduce(output, opts=ReduceOp.AVG) | |||
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Can we add a comment discussing why we need to use this call instead of the original one? This is less intuitive.
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Sure I will add a comment, this is due to these changes (pytorch/pytorch@35c45a4#diff-61109d1cb2a0bd13fc51d678a82666295289da1ec0a1a694e73d9e8c28f51bdcR2885, so the regular dist.all_reduce() is no longer compatible
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@H-Huang can we fix this in the torchft side? We should just be able to ignore the case when there's no return work object iiuc
d4l3k
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May 6, 2025
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I was seeing this log / commit failure when using FT:
should_commit=False enough_replicas=True, errored='NoneType' object has no attribute 'wait’It was coming from an FSDP hook which was calling
dist.allreduce()the regular c10d collective now returnsNonewhich causes the error above. Instead we should be usingself.replicate_pg.allreduce(output, opts=ReduceOp.AVG). I think we could also achieve the same thing withmanager.allreduce(output), so I'm not sure if theManagedProcessGroupis needed. Would appreciate any thoughts @fegin @d4l3k