improve pickle tests for callbacks (#1717)

* improve pickle tests for callbacks

* set mode dict as a class attr

pytorch_lightning/callbacks/early_stopping.py

@@ -45,11 +45,14 @@ class EarlyStopping(Callback):
         >>> early_stopping = EarlyStopping('val_loss')
         >>> trainer = Trainer(early_stop_callback=early_stopping)
     """
+    mode_dict = {
+        'min': torch.lt,
+        'max': torch.gt,
+    }
 
     def __init__(self, monitor: str = 'val_loss', min_delta: float = 0.0, patience: int = 3,
                  verbose: bool = False, mode: str = 'auto', strict: bool = True):
         super().__init__()
-
         self.monitor = monitor
         self.patience = patience
         self.verbose = verbose
@@ -59,17 +62,19 @@ class EarlyStopping(Callback):
         self.stopped_epoch = 0
         self.mode = mode
 
-        mode_dict = {
-            'min': torch.lt,
-            'max': torch.gt,
-            'auto': torch.gt if 'acc' in self.monitor else torch.lt
-        }
-
-        if mode not in mode_dict:
+        if mode not in self.mode_dict:
             if self.verbose > 0:
                 log.info(f'EarlyStopping mode {mode} is unknown, fallback to auto mode.')
             self.mode = 'auto'
 
+        if self.mode == 'auto':
+            if self.monitor == 'acc':
+                self.mode = 'max'
+            else:
+                self.mode = 'min'
+            if self.verbose > 0:
+                log.info(f'EarlyStopping mode set to {self.mode} for monitoring {self.monitor}.')
+
         self.min_delta *= 1 if self.monitor_op == torch.gt else -1
 
     def _validate_condition_metric(self, logs):
@@ -96,12 +101,7 @@ class EarlyStopping(Callback):
 
     @property
     def monitor_op(self):
-        mode_dict = {
-            'min': torch.lt,
-            'max': torch.gt,
-            'auto': torch.gt if 'acc' in self.monitor else torch.lt
-        }
-        return mode_dict[self.mode]
+        return self.mode_dict[self.mode]
 
     def on_train_start(self, trainer, pl_module):
         # Allow instances to be re-used

tests/callbacks/test_callbacks.py

@@ -229,8 +229,14 @@ def test_pickling(tmpdir):
     early_stopping = EarlyStopping()
     ckpt = ModelCheckpoint(tmpdir)
 
-    pickle.dumps(ckpt)
-    pickle.dumps(early_stopping)
+    early_stopping_pickled = pickle.dumps(early_stopping)
+    ckpt_pickled = pickle.dumps(ckpt)
+
+    early_stopping_loaded = pickle.loads(early_stopping_pickled)
+    ckpt_loaded = pickle.loads(ckpt_pickled)
+
+    assert vars(early_stopping) == vars(early_stopping_loaded)
+    assert vars(ckpt) == vars(ckpt_loaded)
 
 
 @pytest.mark.parametrize('save_top_k', [-1, 0, 1, 2])