Internal change

PiperOrigin-RevId: 355065007

official/core/base_trainer.py

@@ -320,9 +320,12 @@ class Trainer(orbit.StandardTrainer, orbit.StandardEvaluator):
       # `self.validation_loss` metric was not updated, because the validation
       # loss was not returned from the task's `validation_step` method.
       logging.info("The task did not report validation loss.")
-    if aggregated_logs:
-      metrics = self.task.reduce_aggregated_logs(aggregated_logs)
-      logs.update(metrics)
+
+    # Merges additional metrics from `reduce_aggregated_logs` method.
+    # By default, the method in `base_task.Task` returns an empty dict, while
+    # the subclass may override it to return metrics computed on host.
+    metrics = self.task.reduce_aggregated_logs(aggregated_logs)
+    logs.update(metrics)
 
     if self._checkpoint_exporter:
       self._checkpoint_exporter.maybe_export_checkpoint(