fixed #854 EarlyStoppingCallback considers first epoch as bad

CHANGELOG.md

@@ -31,6 +31,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - `.dependabot/config.yml` contained invalid details ([#781](https://github.com/catalyst-team/catalyst/issues/781))
 - `LanguageModelingDataset` ([#841](https://github.com/catalyst-team/catalyst/pull/841))
+- EarlyStoppingCallback considers first epoch as bad
+ ([#854](https://github.com/catalyst-team/catalyst/issues/854))
+
 
 ## [20.06] - 2020-06-04
 

catalyst/core/callbacks/early_stop.py

@@ -51,9 +51,7 @@ def on_epoch_end(self, runner: IRunner) -> None:
             return
 
         score = runner.valid_metrics[self.metric]
-        if self.best_score is None:
-            self.best_score = score
-        if self.is_better(score, self.best_score):
+        if self.best_score is None or self.is_better(score, self.best_score):
             self.num_bad_epochs = 0
             self.best_score = score
         else:

catalyst/core/callbacks/tests/test_early_stop.py

@@ -0,0 +1,17 @@
+from unittest.mock import MagicMock, PropertyMock
+
+from catalyst.core import EarlyStoppingCallback
+
+
+def test_patience1():
+    """@TODO: Docs. Contribution is welcome."""
+    early_stop = EarlyStoppingCallback(1)
+    runner = MagicMock()
+    type(runner).stage_name = PropertyMock(return_value="training")
+    type(runner).valid_metrics = PropertyMock(return_value={"loss": 0.001})
+    stop_mock = PropertyMock(return_value=False)
+    type(runner).need_early_stop = stop_mock
+
+    early_stop.on_epoch_end(runner)
+
+    assert stop_mock.mock_calls == []