Fix PPFormulaNet training loss: prevent incorrect label shift in ForCausalLMLoss - #47319
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Fix PPFormulaNet training loss: prevent incorrect label shift in ForCausalLMLoss#47319sagnikai wants to merge 1 commit into
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ForCausalLMLoss internally shifts labels left by 1 (labels[..., 1:]) when shift_labels is not provided. However, PPFormulaNet is an encoder-decoder model where logits are already aligned with labels — no shift is needed. This causes the model to train against misaligned labels, losing the last target token.
This fix passes shift_labels=labels to ForCausalLMLoss, telling it to skip the internal shift. This matches the same pattern used by Florence2 (fixed in #46898), which PPFormulaNet inherits from but overrides orward().
Fixes #47317.