Fix bug in examples: double wrap into DataParallel during eval

examples/mm-imdb/run_mmimdb.py

@@ -278,7 +278,7 @@ def evaluate(args, model, tokenizer, criterion, prefix=""):
     )
 
     # multi-gpu eval
-    if args.n_gpu > 1:
+    if args.n_gpu > 1 and not isinstance(model, torch.nn.DataParallel):
         model = torch.nn.DataParallel(model)
 
     # Eval!