SyncBN raise ERROR when count = 1
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- Python
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Description
It is right that BN layer in torch.nn raises error when count = 1 (only 1 value per channel).
However, for SyncBN layer, even that count = 1 for one GPU, it should NOT raise the error when mean and var are synchronized across multiple GPUs.
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Research direction
Start with the count check at lines 29–30 of apex/parallel/optimized_sync_batchnorm_kernel.py and trace how SyncBN synchronizes mean and variance across GPUs. Reproduce the count=1-per-GPU case, then verify that the error is avoided when the synchronized aggregate has enough values while the single-value case remains rejected.
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Assessment
- Tech stack
- python, pytorch
- Domain
- distributed-systems, machine-learning
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100