[s2s] support early stopping based on loss, rather than rouge (#6927)

examples/seq2seq/test_seq2seq_examples.py

@@ -33,7 +33,7 @@ CUDA_AVAILABLE = torch.cuda.is_available()
 CHEAP_ARGS = {
     "label_smoothing": 0.2,
     "eval_beams": 1,
-    "val_metric": None,
+    "val_metric": "loss",
     "save_top_k": 1,
     "adafactor": True,
     "early_stopping_patience": 2,
@@ -262,9 +262,9 @@ class TestSummarizationDistiller(unittest.TestCase):
         if not check_contents:
             return model
         contents = os.listdir(output_dir)
-        ckpt_name = "val_avg_rouge2=0.0000-step_count=2.ckpt"  # "val_avg_rouge2=0.0000-epoch=1.ckpt"  # "epoch=1-val_avg_rouge2=0.0000.ckpt"
         contents = {os.path.basename(p) for p in contents}
-        self.assertIn(ckpt_name, contents)
+        ckpt_files = [p for p in contents if p.endswith("ckpt")]
+        assert len(ckpt_files) > 0
 
         self.assertIn("test_generations.txt", contents)
         self.assertIn("test_results.txt", contents)