[v0] Fix reward model training safetensors saving (#10137)

src/llamafactory/train/rm/trainer.py

@@ -109,6 +109,27 @@ class PairwiseTrainer(Trainer):
         else:
             return loss
 
+    @override
+    def _save(self, output_dir: Optional[str] = None, state_dict=None):
+        if state_dict is None:
+            state_dict = self.model.state_dict()
+
+        if self.args.save_safetensors:
+            from collections import defaultdict
+
+            ptrs = defaultdict(list)
+            for name, tensor in state_dict.items():
+                if isinstance(tensor, torch.Tensor):
+                    ptrs[id(tensor)].append(name)
+
+            for names in ptrs.values():
+                if len(names) > 1:
+                    names.sort()
+                    for name in names[1:]:
+                        state_dict.pop(name, None)
+
+        super()._save(output_dir, state_dict)
+
     def save_predictions(self, predict_results: "PredictionOutput") -> None:
         r"""Save model predictions to `output_dir`.