fix distdataloader, fix eval with dp group (PaddlePaddle#8420)

Author: DesmonDay

paddlenlp/data/dist_dataloader.py

@@ -171,8 +171,6 @@ def _broadcast_data(self, data):
                 src=self._pp_group.ranks[0],
                 group=self._pp_group,
             )
-        else:
-            fake_data = [None]
 
         fake_data = fake_data[0]
         if fake_data is None:

paddlenlp/trainer/trainer.py

@@ -1434,15 +1434,15 @@ def get_eval_dataloader(self, eval_dataset: Optional[Dataset] = None) -> DataLoa
                     eval_dataset,
                     batch_size=self.args.per_device_eval_batch_size,
                     collate_fn=self.data_collator,
-                    num_workers=self.args.dataloader_num_workers,
+                    num_workers=0,
                     eval=True,
                 )
             else:
                 return DataLoader(
                     eval_dataset,
                     batch_size=self.args.per_device_eval_batch_size,
                     collate_fn=self.data_collator,
-                    num_workers=self.args.dataloader_num_workers,
+                    num_workers=0,
                 )
 
         eval_sampler = self._get_eval_sampler(eval_dataset)