PyTorch Compilation Pitfall: FSDP Guard Skipping Hurts MFU

SeunghyunSEO7 · x · 2026-08-24

A developer discovered that when using torch.compile with dynamic shape=True for the Flux.2 klein image model, PyTorch automatically skips installing guards for FSDP wrapped modules. This behavior significantly hurts Model FLOPs Utilization (MFU), serving as a warning for multi-resolution training setups.

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