fix: ensure dtype consistency in grouped_mm under autocast#43833
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nulone wants to merge 2 commits into
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fix: ensure dtype consistency in grouped_mm under autocast#43833nulone wants to merge 2 commits into
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torch._grouped_mm is not registered for autocast, causing dtype mismatch when LayerNorm outputs float32 but weights are bfloat16. Fixes huggingface#43828
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ArthurZucker
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Feb 9, 2026
ArthurZucker
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Hey! does not look too bad, just unsure, should we cast back post op?
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No need — the result is already cast back to https://github.com/huggingface/transformers/blob/main/src/transformers/integrations/moe.py#L273 So the dtype flow is: input (float32) → cast to weight.dtype (bf16) → _grouped_mm → cast back to hidden_states.dtype (float32) at the end. |
This was referenced Apr 29, 2026
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Fixes #43828
What does this PR do?
torch._grouped_mmis not registered for autocast. Undertorch.autocast, LayerNorm outputs float32 while model weights stay bfloat16, causing RuntimeError: "expected mat1 and mat2 to have same dtype".Fix
Cast input to
weight.dtypebefore calling_grouped_mminsrc/transformers/integrations/moe.py.Impact
Affects all MoE models using
grouped_mmunder autocast (Mixtral, Qwen3 MoE, DeepSeek, PhiMoE, etc.)Before submitting
Note: No local GPU access — relying on CI for verification.