Files
AstrAI/astrai/parallel
ViperEkura 8206afefd9 fix: FSDP clip_grad_norm and default reshard_after_forward=False
- FSDP params are DTensors sharded across ranks
- torch.nn.utils.clip_grad_norm_ computes LOCAL norm only
- Each rank would clip by a different factor, causing gradient divergence
- Fix: compute local norm, all-reduce squared sum, sqrt for global norm
- Default reshard_after_forward=False (forward then backward makes reshard redundant)
- Reduces per-step time by ~19% (1033ms to 839ms on 2xL20)
2026-07-29 23:27:10 +08:00
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