Merge pull request #1595 from MattiaFanan/fix-EarlyStoppingPlugin

Fix early stopping plugin

avalanche/training/plugins/early_stopping.py

@@ -115,18 +115,20 @@ def _update_best(self, strategy):
                 f"Metric {self.metric_name} used by the EarlyStopping plugin "
                 f"is not computed yet. EarlyStopping will not be triggered."
             )
-        if self.best_val is None or self.operator(val_acc, self.best_val):
+
+        if self.best_val is None:
+            self.best_state = deepcopy(strategy.model.state_dict())
+            self.best_val = val_acc
+            self.best_step = self._get_strategy_counter(strategy)
+            return None
+
+        delta_val = float(val_acc - self.best_val)
+        if self.operator(delta_val, 0) and abs(delta_val) >= self.margin:
             self.best_state = deepcopy(strategy.model.state_dict())
-            if self.best_val is None:
-                self.best_val = val_acc
-                self.best_step = 0
-                return None
-
-            if self.operator(float(val_acc - self.best_val), self.margin):
-                self.best_step = self._get_strategy_counter(strategy)
-                self.best_val = val_acc
-                if self.verbose:
-                    print("EarlyStopping: new best value:", val_acc)
+            self.best_val = val_acc
+            self.best_step = self._get_strategy_counter(strategy)
+            if self.verbose:
+                print("EarlyStopping: new best value:", val_acc)
 
         return self.best_val