Update all hf examples to have dist.barrier #1139
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kwen2501
approved these changes
Aug 21, 2024
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LGTM. Thanks!
Pasting our triage here for future reference:
If the batch is small, and the two ranks have a gap in terms of when they are launched, then rank 0 could have finished sending the activations before rank 1 bootstraps.
(In NCCL, sending a small message does not need handshake between the two ranks)
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Without having
dist.barrier(), all of the HF examples wind up hanging since we're destroying the pg before all comms have completed in these small examples, leading to a hang. This PR addsdist.barrier()just beforedist.destroy_process_group()to fix this.