[Enhance] Support dynamic interval (#342)

* support dynamic interval in iterbasedtrainloop

* update typehint

* update typehint

* add dynamic interval in epochbasedtrainloop

* update

* fix

Co-authored-by: luochunhua.vendor <luochunhua@pjlab.org.cn>

mmengine/runner/loops.py

 # Copyright (c) OpenMMLab. All rights reserved.
+import bisect
 import time
 import warnings
-from typing import Dict, List, Sequence, Union
+from typing import Dict, List, Optional, Sequence, Tuple, Union
 
 import torch
 from torch.utils.data import DataLoader
@@ -11,6 +12,7 @@ from mmengine.registry import LOOPS
 from mmengine.utils import is_list_of
 from .amp import autocast
 from .base_loop import BaseLoop
+from .utils import calc_dynamic_intervals
 
 
 @LOOPS.register_module()
@@ -25,14 +27,20 @@ class EpochBasedTrainLoop(BaseLoop):
         val_begin (int): The epoch that begins validating.
             Defaults to 1.
         val_interval (int): Validation interval. Defaults to 1.
+        dynamic_intervals (List[Tuple[int, int]], optional): The
+            first element in the tuple is a milestone and the second
+            element is a interval. The interval is used after the
+            corresponding milestone. Defaults to None.
     """
 
-    def __init__(self,
-                 runner,
-                 dataloader: Union[DataLoader, Dict],
-                 max_epochs: int,
-                 val_begin: int = 1,
-                 val_interval: int = 1) -> None:
+    def __init__(
+            self,
+            runner,
+            dataloader: Union[DataLoader, Dict],
+            max_epochs: int,
+            val_begin: int = 1,
+            val_interval: int = 1,
+            dynamic_intervals: Optional[List[Tuple[int, int]]] = None) -> None:
         super().__init__(runner, dataloader)
         self._max_epochs = max_epochs
         self._max_iters = max_epochs * len(self.dataloader)
@@ -49,6 +57,10 @@ class EpochBasedTrainLoop(BaseLoop):
                 'metainfo. ``dataset_meta`` in visualizer will be '
                 'None.')
 
+        self.dynamic_milestones, self.dynamic_intervals = \
+            calc_dynamic_intervals(
+                self.val_interval, dynamic_intervals)
+
     @property
     def max_epochs(self):
         """int: Total epochs to train model."""
@@ -76,6 +88,7 @@ class EpochBasedTrainLoop(BaseLoop):
         while self._epoch < self._max_epochs:
             self.run_epoch()
 
+            self._decide_current_val_interval()
             if (self.runner.val_loop is not None
                     and self._epoch >= self.val_begin
                     and self._epoch % self.val_interval == 0):
@@ -114,6 +127,11 @@ class EpochBasedTrainLoop(BaseLoop):
             outputs=outputs)
         self._iter += 1
 
+    def _decide_current_val_interval(self) -> None:
+        """Dynamically modify the ``val_interval``."""
+        step = bisect.bisect(self.dynamic_milestones, (self.epoch + 1))
+        self.val_interval = self.dynamic_intervals[step - 1]
+
 
 class _InfiniteDataloaderIterator:
     """An infinite dataloader iterator wrapper for IterBasedTrainLoop.
@@ -172,14 +190,20 @@ class IterBasedTrainLoop(BaseLoop):
         val_begin (int): The iteration that begins validating.
             Defaults to 1.
         val_interval (int): Validation interval. Defaults to 1000.
+        dynamic_intervals (List[Tuple[int, int]], optional): The
+            first element in the tuple is a milestone and the second
+            element is a interval. The interval is used after the
+            corresponding milestone. Defaults to None.
     """
 
-    def __init__(self,
-                 runner,
-                 dataloader: Union[DataLoader, Dict],
-                 max_iters: int,
-                 val_begin: int = 1,
-                 val_interval: int = 1000) -> None:
+    def __init__(
+            self,
+            runner,
+            dataloader: Union[DataLoader, Dict],
+            max_iters: int,
+            val_begin: int = 1,
+            val_interval: int = 1000,
+            dynamic_intervals: Optional[List[Tuple[int, int]]] = None) -> None:
         super().__init__(runner, dataloader)
         self._max_iters = max_iters
         self._max_epochs = 1  # for compatibility with EpochBasedTrainLoop
@@ -198,6 +222,10 @@ class IterBasedTrainLoop(BaseLoop):
         # get the iterator of the dataloader
         self.dataloader_iterator = _InfiniteDataloaderIterator(self.dataloader)
 
+        self.dynamic_milestones, self.dynamic_intervals = \
+            calc_dynamic_intervals(
+                self.val_interval, dynamic_intervals)
+
     @property
     def max_epochs(self):
         """int: Total epochs to train model."""
@@ -230,6 +258,7 @@ class IterBasedTrainLoop(BaseLoop):
             data_batch = next(self.dataloader_iterator)
             self.run_iter(data_batch)
 
+            self._decide_current_val_interval()
             if (self.runner.val_loop is not None
                     and self._iter >= self.val_begin
                     and self._iter % self.val_interval == 0):
@@ -260,6 +289,11 @@ class IterBasedTrainLoop(BaseLoop):
             outputs=outputs)
         self._iter += 1
 
+    def _decide_current_val_interval(self) -> None:
+        """Dynamically modify the ``val_interval``."""
+        step = bisect.bisect(self.dynamic_milestones, (self._iter + 1))
+        self.val_interval = self.dynamic_intervals[step - 1]
+
 
 @LOOPS.register_module()
 class ValLoop(BaseLoop):

mmengine/runner/utils.py

+# Copyright (c) OpenMMLab. All rights reserved.
+from typing import List, Optional, Tuple
+
+from mmengine.utils.misc import is_list_of
+
+
+def calc_dynamic_intervals(
+    start_interval: int,
+    dynamic_interval_list: Optional[List[Tuple[int, int]]] = None
+) -> Tuple[List[int], List[int]]:
+    """Calculate dynamic intervals.
+
+    Args:
+        start_interval (int): The interval used in the beginning.
+        dynamic_interval_list (List[Tuple[int, int]], optional): The
+            first element in the tuple is a milestone and the second
+            element is a interval. The interval is used after the
+            corresponding milestone. Defaults to None.
+
+    Returns:
+        Tuple[List[int], List[int]]: a list of milestone and its corresponding
+            intervals.
+    """
+    if dynamic_interval_list is None:
+        return [0], [start_interval]
+
+    assert is_list_of(dynamic_interval_list, tuple)
+
+    dynamic_milestones = [0]
+    dynamic_milestones.extend(
+        [dynamic_interval[0] for dynamic_interval in dynamic_interval_list])
+    dynamic_intervals = [start_interval]
+    dynamic_intervals.extend(
+        [dynamic_interval[1] for dynamic_interval in dynamic_interval_list])
+    return dynamic_milestones, dynamic_intervals

tests/test_runner/test_runner.py

@@ -1283,6 +1283,80 @@ class TestRunner(TestCase):
                                    val_batch_idx_targets):
             self.assertEqual(result, target)
 
+        # 5. test dynamic interval in IterBasedTrainLoop
+        max_iters = 12
+        interval = 5
+        dynamic_intervals = [(11, 2)]
+        iter_results = []
+        iter_targets = [5, 10, 12]
+        val_interval_results = []
+        val_interval_targets = [5] * 10 + [2] * 2
+
+        @HOOKS.register_module()
+        class TestIterDynamicIntervalHook(Hook):
+
+            def before_val(self, runner):
+                iter_results.append(runner.iter)
+
+            def before_train_iter(self, runner, batch_idx, data_batch=None):
+                val_interval_results.append(runner.train_loop.val_interval)
+
+        cfg = copy.deepcopy(self.iter_based_cfg)
+        cfg.experiment_name = 'test_train5'
+        cfg.train_dataloader.sampler = dict(
+            type='DefaultSampler', shuffle=True)
+        cfg.custom_hooks = [
+            dict(type='TestIterDynamicIntervalHook', priority=50)
+        ]
+        cfg.train_cfg = dict(
+            by_epoch=False,
+            max_iters=max_iters,
+            val_interval=interval,
+            dynamic_intervals=dynamic_intervals)
+        runner = Runner.from_cfg(cfg)
+        runner.train()
+        for result, target, in zip(iter_results, iter_targets):
+            self.assertEqual(result, target)
+        for result, target, in zip(val_interval_results, val_interval_targets):
+            self.assertEqual(result, target)
+
+        # 6. test dynamic interval in EpochBasedTrainLoop
+        max_epochs = 12
+        interval = 5
+        dynamic_intervals = [(11, 2)]
+        epoch_results = []
+        epoch_targets = [5, 10, 12]
+        val_interval_results = []
+        val_interval_targets = [5] * 10 + [2] * 2
+
+        @HOOKS.register_module()
+        class TestEpochDynamicIntervalHook(Hook):
+
+            def before_val_epoch(self, runner):
+                epoch_results.append(runner.epoch)
+
+            def before_train_epoch(self, runner):
+                val_interval_results.append(runner.train_loop.val_interval)
+
+        cfg = copy.deepcopy(self.epoch_based_cfg)
+        cfg.experiment_name = 'test_train6'
+        cfg.train_dataloader.sampler = dict(
+            type='DefaultSampler', shuffle=True)
+        cfg.custom_hooks = [
+            dict(type='TestEpochDynamicIntervalHook', priority=50)
+        ]
+        cfg.train_cfg = dict(
+            by_epoch=True,
+            max_epochs=max_epochs,
+            val_interval=interval,
+            dynamic_intervals=dynamic_intervals)
+        runner = Runner.from_cfg(cfg)
+        runner.train()
+        for result, target, in zip(epoch_results, epoch_targets):
+            self.assertEqual(result, target)
+        for result, target, in zip(val_interval_results, val_interval_targets):
+            self.assertEqual(result, target)
+
     def test_val(self):
         cfg = copy.deepcopy(self.epoch_based_cfg)
         cfg.experiment_name = 'test_val1'