Improve mismatched sizes management when loading a pretrained model (#17257)

- Add --ignore_mismatched_sizes argument to classification examples

- Expand the error message when loading a model whose head dimensions are different from expected dimensions

examples/pytorch/text-classification/README.md

@@ -22,7 +22,7 @@ Based on the script [`run_glue.py`](https://github.com/huggingface/transformers/
 
 Fine-tuning the library models for sequence classification on the GLUE benchmark: [General Language Understanding
 Evaluation](https://gluebenchmark.com/). This script can fine-tune any of the models on the [hub](https://huggingface.co/models)
-and can also be used for a dataset hosted on our [hub](https://huggingface.co/datasets) or your own data in a csv or a JSON file 
+and can also be used for a dataset hosted on our [hub](https://huggingface.co/datasets) or your own data in a csv or a JSON file
 (the script might need some tweaks in that case, refer to the comments inside for help).
 
 GLUE is made up of a total of 9 different tasks. Here is how to run the script on one of them:
@@ -79,6 +79,8 @@ python run_glue.py \
   --output_dir /tmp/imdb/
 ```
 
+> If your model classification head dimensions do not fit the number of labels in the dataset, you can specify `--ignore_mismatched_sizes` to adapt it.
+
 
 ### Mixed precision training
 

examples/pytorch/text-classification/run_glue.py

@@ -196,6 +196,10 @@ class ModelArguments:
             )
         },
     )
+    ignore_mismatched_sizes: bool = field(
+        default=False,
+        metadata={"help": "Will enable to load a pretrained model whose head dimensions are different."},
+    )
 
 
 def main():
@@ -364,6 +368,7 @@ def main():
         cache_dir=model_args.cache_dir,
         revision=model_args.model_revision,
         use_auth_token=True if model_args.use_auth_token else None,
+        ignore_mismatched_sizes=model_args.ignore_mismatched_sizes,
     )
 
     # Preprocessing the raw_datasets

examples/pytorch/text-classification/run_glue_no_trainer.py

@@ -170,6 +170,11 @@ def parse_args():
         action="store_true",
         help="Whether to load in all available experiment trackers from the environment and use them for logging.",
     )
+    parser.add_argument(
+        "--ignore_mismatched_sizes",
+        action="store_true",
+        help="Whether or not to enable to load a pretrained model whose head dimensions are different.",
+    )
     args = parser.parse_args()
 
     # Sanity checks
@@ -288,6 +293,7 @@ def main():
         args.model_name_or_path,
         from_tf=bool(".ckpt" in args.model_name_or_path),
         config=config,
+        ignore_mismatched_sizes=args.ignore_mismatched_sizes,
     )
 
     # Preprocessing the datasets

examples/pytorch/text-classification/run_xnli.py

@@ -162,6 +162,10 @@ class ModelArguments:
             )
         },
     )
+    ignore_mismatched_sizes: bool = field(
+        default=False,
+        metadata={"help": "Will enable to load a pretrained model whose head dimensions are different."},
+    )
 
 
 def main():
@@ -291,6 +295,7 @@ def main():
         cache_dir=model_args.cache_dir,
         revision=model_args.model_revision,
         use_auth_token=True if model_args.use_auth_token else None,
+        ignore_mismatched_sizes=model_args.ignore_mismatched_sizes,
     )
 
     # Preprocessing the datasets