[trainer] fix pt loss (#7748)

* fix pt loss

* robust

* fix

* test

src/llamafactory/train/pt/trainer.py

@@ -40,6 +40,11 @@ class CustomTrainer(Trainer):
             kwargs["processing_class"] = kwargs.pop("tokenizer")
 
         super().__init__(**kwargs)
+        if processor is not None:
+            # avoid wrong loss under gradient accumulation
+            # https://github.com/huggingface/transformers/pull/36044#issuecomment-2746657112
+            self.model_accepts_loss_kwargs = False
+
         self.finetuning_args = finetuning_args
 
         if processor is not None:

src/llamafactory/train/sft/trainer.py

@@ -60,6 +60,8 @@ class CustomSeq2SeqTrainer(Seq2SeqTrainer):
 
         super().__init__(**kwargs)
         if processor is not None:
+            # avoid wrong loss under gradient accumulation
+            # https://github.com/huggingface/transformers/pull/36044#issuecomment-2746657112
             self.model_accepts_loss_kwargs = False
 
         self.finetuning_args = finetuning_args