fix: torch.checkpoint() incorrectly wraps single forward step in original codebase. #274
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Bug Fixes:
Fixes bugs that caused the loss to remain high due to unstable gradients when training with gradient checkpointing enabled. After fixing, the acceptance rate increases as intended when using the gradient checkpoint memory optimization trick.
Modification:
Refactors the draft model’s forward function by separating target model hidden state retrieval and the draft model’s layer flow. Wraps the entire training-time test predictions over the drafting length, removing the torch.checkpoint() loops that previously led to a complicated computation graph and incorrect gradient flows.