Fix RNG reload in resume training from epoch checkpoint#17055
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atreyasha
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May 3, 2022
tests/trainer/test_trainer.py
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| # For more than 1 GPUs, since the randomness is introduced in the model and with DataParallel (which is used | ||
| # in this test for more than 2 GPUs), the calls to the torch RNG will happen in a random order (sometimes | ||
| # GPU 0 will call first and sometimes GPU 1). | ||
| random_torch = torch.cuda.is_available() and torch.cuda.device_count() >= 1 |
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Sorry, just a question regarding this line. AFAICT random_torch would only be True if at least one GPU is available. But this would mean this test case will not cover torch randomness when using the CPU. The unit test before this commit however did test randomness on the CPU, or at least was able to if no GPU was available. Is this change intended?
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Good catch! I'll fix this :-)
stevhliu
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May 3, 2022
…17055) * Fix RNG reload in resume training from epoch checkpoint * Fix test
elusenji
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Jun 12, 2022
…17055) * Fix RNG reload in resume training from epoch checkpoint * Fix test
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What does this PR do?
This PR fixes the reproducibility in training when checkpoints are saved every epoch. The main reason it was failing (as pointed out in #17032) is that the RNG states were never reloaded. They need to be reloaded exactly before iterating through the new epoch, as the call to this will change the global PyTorch RNG (even if the dataloader uses its own generator...) The new test added makes sure this reproducibility is fully tested.
While debugging this, two issues occurred, which this PR also fixes.
DataParallel(an issue that wouldn't be the case withDistributedDataParallelbut we would need to execute the test via a launcher in that case). So in the test, we only do PyTorch randomness on one or zero GPU to fix this flakiness.Fixes #17032