Distributed eval: SequentialDistributedSampler + gather all results (#4243)

* Distributed eval: SequentialDistributedSampler + gather all results

* For consistency only write to disk from world_master

Close https://github.com/huggingface/transformers/issues/4272

* Working distributed eval

* Hook into scripts

* Fix #3721 again

* TPU.mesh_reduce: stay in tensor space

Thanks @jysohn23

* Just a small comment

* whitespace

* torch.hub: pip install packaging

* Add test scenarii

examples/text-classification/run_glue.py

@@ -166,7 +166,7 @@ def main():
 
     # Evaluation
     results = {}
-    if training_args.do_eval and training_args.local_rank in [-1, 0]:
+    if training_args.do_eval:
         logger.info("*** Evaluate ***")
 
         # Loop to handle MNLI double evaluation (matched, mis-matched)
@@ -181,11 +181,12 @@ def main():
             output_eval_file = os.path.join(
                 training_args.output_dir, f"eval_results_{eval_dataset.args.task_name}.txt"
             )
-            with open(output_eval_file, "w") as writer:
-                logger.info("***** Eval results {} *****".format(eval_dataset.args.task_name))
-                for key, value in result.items():
-                    logger.info("  %s = %s", key, value)
-                    writer.write("%s = %s\n" % (key, value))
+            if trainer.is_world_master():
+                with open(output_eval_file, "w") as writer:
+                    logger.info("***** Eval results {} *****".format(eval_dataset.args.task_name))
+                    for key, value in result.items():
+                        logger.info("  %s = %s", key, value)
+                        writer.write("%s = %s\n" % (key, value))
 
             results.update(result)