[Enhance] Return loop results. (#392)

mmengine/runner/base_loop.py

@@ -1,6 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 from abc import ABCMeta, abstractmethod
-from typing import Dict, Union
+from typing import Any, Dict, Union
 
 from torch.utils.data import DataLoader
 
@@ -33,5 +33,5 @@ class BaseLoop(metaclass=ABCMeta):
         return self._runner
 
     @abstractmethod
-    def run(self) -> None:
+    def run(self) -> Any:
         """Execute loop."""

mmengine/runner/loops.py

@@ -81,7 +81,7 @@ class EpochBasedTrainLoop(BaseLoop):
         """int: Current iteration."""
         return self._iter
 
-    def run(self) -> None:
+    def run(self) -> torch.nn.Module:
         """Launch training."""
         self.runner.call_hook('before_train')
 
@@ -95,6 +95,7 @@ class EpochBasedTrainLoop(BaseLoop):
                 self.runner.val_loop.run()
 
         self.runner.call_hook('after_train')
+        return self.runner.model
 
     def run_epoch(self) -> None:
         """Iterate one epoch."""
@@ -266,6 +267,7 @@ class IterBasedTrainLoop(BaseLoop):
 
         self.runner.call_hook('after_train_epoch')
         self.runner.call_hook('after_train')
+        return self.runner.model
 
     def run_iter(self, data_batch: Sequence[dict]) -> None:
         """Iterate one mini-batch.
@@ -330,7 +332,7 @@ class ValLoop(BaseLoop):
                 'visualizer will be None.')
         self.fp16 = fp16
 
-    def run(self):
+    def run(self) -> dict:
         """Launch validation."""
         self.runner.call_hook('before_val')
         self.runner.call_hook('before_val_epoch')
@@ -342,6 +344,7 @@ class ValLoop(BaseLoop):
         metrics = self.evaluator.evaluate(len(self.dataloader.dataset))
         self.runner.call_hook('after_val_epoch', metrics=metrics)
         self.runner.call_hook('after_val')
+        return metrics
 
     @torch.no_grad()
     def run_iter(self, idx, data_batch: Sequence[dict]):
@@ -399,7 +402,7 @@ class TestLoop(BaseLoop):
                 'visualizer will be None.')
         self.fp16 = fp16
 
-    def run(self) -> None:
+    def run(self) -> dict:
         """Launch test."""
         self.runner.call_hook('before_test')
         self.runner.call_hook('before_test_epoch')
@@ -411,6 +414,7 @@ class TestLoop(BaseLoop):
         metrics = self.evaluator.evaluate(len(self.dataloader.dataset))
         self.runner.call_hook('after_test_epoch', metrics=metrics)
         self.runner.call_hook('after_test')
+        return metrics
 
     @torch.no_grad()
     def run_iter(self, idx, data_batch: Sequence[dict]) -> None:

mmengine/runner/runner.py

@@ -1595,8 +1595,12 @@ class Runner:
             self.load_checkpoint(self._load_from)
             self._has_loaded = True
 
-    def train(self) -> None:
-        """Launch training."""
+    def train(self) -> nn.Module:
+        """Launch training.
+
+        Returns:
+            nn.Module: The model after training.
+        """
         if self._train_loop is None:
             raise RuntimeError(
                 '`self._train_loop` should not be None when calling train '
@@ -1634,11 +1638,16 @@ class Runner:
             self._train_loop.iter,  # type: ignore
             self._train_loop.max_iters)  # type: ignore
 
-        self.train_loop.run()  # type: ignore
+        model = self.train_loop.run()  # type: ignore
         self.call_hook('after_run')
+        return model
 
-    def val(self) -> None:
-        """Launch validation."""
+    def val(self) -> dict:
+        """Launch validation.
+
+        Returns:
+            dict: A dict of metrics on validation set.
+        """
         if self._val_loop is None:
             raise RuntimeError(
                 '`self._val_loop` should not be None when calling val method.'
@@ -1652,11 +1661,16 @@ class Runner:
         # make sure checkpoint-related hooks are triggered after `before_run`
         self.load_or_resume()
 
-        self.val_loop.run()  # type: ignore
+        metrics = self.val_loop.run()  # type: ignore
         self.call_hook('after_run')
+        return metrics
 
-    def test(self) -> None:
-        """Launch test."""
+    def test(self) -> dict:
+        """Launch test.
+
+        Returns:
+            dict: A dict of metrics on testing set.
+        """
         if self._test_loop is None:
             raise RuntimeError(
                 '`self._test_loop` should not be None when calling test '
@@ -1670,8 +1684,9 @@ class Runner:
         # make sure checkpoint-related hooks are triggered after `before_run`
         self.load_or_resume()
 
-        self.test_loop.run()  # type: ignore
+        metrics = self.test_loop.run()  # type: ignore
         self.call_hook('after_run')
+        return metrics
 
     def call_hook(self, fn_name: str, **kwargs) -> None:
         """Call all hooks.