[Enhance] Support build evaluator from list of built metric (#423)

* Support build evaluator from list of built metric

* regist evaluator

* fix as comment

* add unit test

mmengine/evaluator/evaluator.py

@@ -2,10 +2,11 @@
 from typing import Iterator, List, Optional, Sequence, Union
 
 from mmengine.data import BaseDataElement
-from ..registry.root import METRICS
+from ..registry.root import EVALUATOR, METRICS
 from .metric import BaseMetric
 
 
+@EVALUATOR.register_module()
 class Evaluator:
     """Wrapper class to compose multiple :class:`BaseMetric` instances.
 
@@ -19,13 +20,10 @@ class Evaluator:
             metrics = [metrics]
         self.metrics: List[BaseMetric] = []
         for metric in metrics:
-            if isinstance(metric, BaseMetric):
-                self.metrics.append(metric)
-            elif isinstance(metric, dict):
+            if isinstance(metric, dict):
                 self.metrics.append(METRICS.build(metric))
             else:
-                raise TypeError('metric should be a dict or a BaseMetric, '
-                                f'but got {metric}.')
+                self.metrics.append(metric)
 
     @property
     def dataset_meta(self) -> Optional[dict]:

mmengine/runner/loops.py

@@ -316,9 +316,12 @@ class ValLoop(BaseLoop):
                  fp16: bool = False) -> None:
         super().__init__(runner, dataloader)
 
-        if isinstance(evaluator, dict) or is_list_of(evaluator, dict):
+        if isinstance(evaluator, dict) or isinstance(evaluator, list):
             self.evaluator = runner.build_evaluator(evaluator)  # type: ignore
         else:
+            assert isinstance(evaluator, Evaluator), (
+                'evaluator must be one of dict, list or Evaluator instance, '
+                f'but got {type(evaluator)}.')
             self.evaluator = evaluator  # type: ignore
         if hasattr(self.dataloader.dataset, 'metainfo'):
             self.evaluator.dataset_meta = self.dataloader.dataset.metainfo

mmengine/runner/runner.py

@@ -38,8 +38,8 @@ from mmengine.registry import (DATA_SAMPLERS, DATASETS, EVALUATOR, HOOKS,
                                DefaultScope, count_registered_modules)
 from mmengine.registry.root import LOG_PROCESSORS
 from mmengine.utils import (TORCH_VERSION, collect_env, digit_version,
-                            get_git_hash, is_list_of, is_seq_of,
-                            revert_sync_batchnorm, set_multi_processing)
+                            get_git_hash, is_seq_of, revert_sync_batchnorm,
+                            set_multi_processing)
 from mmengine.visualization import Visualizer
 from .base_loop import BaseLoop
 from .checkpoint import (_load_checkpoint, _load_checkpoint_to_model,
@@ -1246,13 +1246,14 @@ class Runner:
 
             return param_schedulers
 
-    def build_evaluator(
-            self, evaluator: Union[Dict, List[Dict], Evaluator]) -> Evaluator:
+    def build_evaluator(self, evaluator: Union[Dict, List,
+                                               Evaluator]) -> Evaluator:
         """Build evaluator.
 
         Examples of ``evaluator``::
 
-            evaluator = dict(type='ToyMetric')
+            # evaluator could be a built Evaluator instance
+            evaluator = Evaluator(metrics=[ToyMetric()])
 
             # evaluator can also be a list of dict
             evaluator = [
@@ -1260,6 +1261,14 @@ class Runner:
                 dict(type='ToyEvaluator2')
             ]
 
+            # evaluator can also be a list of built metric
+            evaluator = [ToyMetric1(), ToyMetric2()]
+
+            # evaluator can also be a dict with key metrics
+            evaluator = dict(metrics=ToyMetric())
+            # metric is a list
+            evaluator = dict(metrics=[ToyMetric()])
+
         Args:
             evaluator (Evaluator or dict or list): An Evaluator object or a
                 config dict or list of config dict used to build an Evaluator.
@@ -1272,13 +1281,12 @@ class Runner:
         elif isinstance(evaluator, dict):
             # if `metrics` in dict keys, it means to build customized evalutor
             if 'metrics' in evaluator:
-                assert 'type' in evaluator, 'expected customized evaluator' \
-                                    f' with key `type`, but got {evaluator}'
+                evaluator.setdefault('type', 'Evaluator')
                 return EVALUATOR.build(evaluator)
             # otherwise, default evalutor will be built
             else:
                 return Evaluator(evaluator)  # type: ignore
-        elif is_list_of(evaluator, dict):
+        elif isinstance(evaluator, list):
             # use the default `Evaluator`
             return Evaluator(evaluator)  # type: ignore
         else:

tests/test_runner/test_runner.py

@@ -1094,6 +1094,12 @@ class TestRunner(TestCase):
         evaluator = [dict(type='ToyMetric1'), dict(type='ToyMetric2')]
         self.assertIsInstance(runner.build_evaluator(evaluator), Evaluator)
 
+        # input is a list of built metric.
+        metric = [ToyMetric1(), ToyMetric2()]
+        _evaluator = runner.build_evaluator(metric)
+        self.assertIs(_evaluator.metrics[0], metric[0])
+        self.assertIs(_evaluator.metrics[1], metric[1])
+
         # test collect device
         evaluator = [
             dict(type='ToyMetric1', collect_device='cpu'),
@@ -1115,6 +1121,10 @@ class TestRunner(TestCase):
         self.assertEqual(_evaluator.metrics[0].collect_device, 'cpu')
         self.assertEqual(_evaluator.metrics[1].collect_device, 'gpu')
 
+        # test evaluator must be a Evaluator instance
+        with self.assertRaisesRegex(TypeError, 'evaluator should be'):
+            _evaluator = runner.build_evaluator(ToyMetric1())
+
     def test_build_dataloader(self):
         cfg = copy.deepcopy(self.epoch_based_cfg)
         cfg.experiment_name = 'test_build_dataloader'