Fix unfreeze strategies with onecyclelr and reduced lr

CHANGELOG.md

@@ -24,6 +24,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 - Fixed a bug where a loaded `TabularClassifier` or `TabularRegressor` checkpoint could not be served ([#1324](https://github.com/PyTorchLightning/lightning-flash/pull/1324))
 
+- Fixed a bug where the `freeze_unfreeze` and `unfreeze_milestones` finetuning strategies could not be used in tandem with a `onecyclelr` LR scheduler ([#1329](https://github.com/PyTorchLightning/lightning-flash/pull/1329))
+
+- Fixed a bug where the backbone learning rate would be divided by 10 when unfrozen if using the `freeze_unfreeze` or `unfreeze_milestones` strategies ([#1329](https://github.com/PyTorchLightning/lightning-flash/pull/1329))
+
 ## [0.7.4] - 2022-04-27
 
 ### Fixed

flash/core/finetuning.py

@@ -103,6 +103,19 @@ def freeze_before_training(self, pl_module: Union[Module, Iterable[Union[Module,
                     modules = [modules]
                 self.freeze(modules=modules, train_bn=self.train_bn)
 
+    def unfreeze_and_extend_param_group(
+        self,
+        modules: Union[Module, Iterable[Union[Module, Iterable]]],
+        optimizer: Optimizer,
+        train_bn: bool = True,
+    ) -> None:
+        self.make_trainable(modules)
+
+        params = self.filter_params(modules, train_bn=train_bn, requires_grad=True)
+        params = self.filter_on_optimizer(optimizer, params)
+        if params:
+            optimizer.param_groups[0]["params"].extend(params)
+
     def _freeze_unfreeze_function(
         self,
         pl_module: Union[Module, Iterable[Union[Module, Iterable]]],
@@ -117,7 +130,7 @@ def _freeze_unfreeze_function(
 
         modules = self._get_modules_to_freeze(pl_module=pl_module)
         if modules is not None:
-            self.unfreeze_and_add_param_group(
+            self.unfreeze_and_extend_param_group(
                 modules=modules,
                 optimizer=optimizer,
                 train_bn=self.train_bn,
@@ -140,15 +153,15 @@ def _unfreeze_milestones_function(
                 # unfreeze num_layers last layers
 
                 backbone_modules = BaseFinetuning.flatten_modules(modules=modules)[-num_layers:]
-                self.unfreeze_and_add_param_group(
+                self.unfreeze_and_extend_param_group(
                     modules=backbone_modules,
                     optimizer=optimizer,
                     train_bn=self.train_bn,
                 )
             elif epoch == unfreeze_milestones[1]:
                 # unfreeze remaining layers
                 backbone_modules = BaseFinetuning.flatten_modules(modules=modules)[:-num_layers]
-                self.unfreeze_and_add_param_group(
+                self.unfreeze_and_extend_param_group(
                     modules=backbone_modules,
                     optimizer=optimizer,
                     train_bn=self.train_bn,

tests/core/test_finetuning.py

@@ -152,20 +152,45 @@ def test_finetuning_with_none_return_type(strategy):
 
 
 @pytest.mark.parametrize(
-    ("strategy", "checker_class", "checker_class_data"),
+    ("strategy", "lr_scheduler", "checker_class", "checker_class_data"),
     [
-        ("no_freeze", None, {}),
-        ("freeze", FreezeStrategyChecking, {}),
-        (("freeze_unfreeze", 2), FreezeUnfreezeStrategyChecking, {"check_epoch": 2}),
+        ("no_freeze", None, None, {}),
+        ("freeze", None, FreezeStrategyChecking, {}),
+        (("freeze_unfreeze", 2), None, FreezeUnfreezeStrategyChecking, {"check_epoch": 2}),
         (
             ("unfreeze_milestones", ((1, 3), 1)),
+            None,
+            UnfreezeMilestonesStrategyChecking,
+            {"check_epochs": [1, 3], "num_layers": 1},
+        ),
+        (
+            "no_freeze",
+            ("onecyclelr", {"max_lr": 1e-3, "epochs": 50, "steps_per_epoch": 10}, {"interval": "step"}),
+            None,
+            {},
+        ),
+        (
+            "freeze",
+            ("onecyclelr", {"max_lr": 1e-3, "epochs": 50, "steps_per_epoch": 10}, {"interval": "step"}),
+            FreezeStrategyChecking,
+            {},
+        ),
+        (
+            ("freeze_unfreeze", 2),
+            ("onecyclelr", {"max_lr": 1e-3, "epochs": 50, "steps_per_epoch": 10}, {"interval": "step"}),
+            FreezeUnfreezeStrategyChecking,
+            {"check_epoch": 2},
+        ),
+        (
+            ("unfreeze_milestones", ((1, 3), 1)),
+            ("onecyclelr", {"max_lr": 1e-3, "epochs": 50, "steps_per_epoch": 10}, {"interval": "step"}),
             UnfreezeMilestonesStrategyChecking,
             {"check_epochs": [1, 3], "num_layers": 1},
         ),
     ],
 )
-def test_finetuning(tmpdir, strategy, checker_class, checker_class_data):
-    task = TestTaskWithFinetuning(loss_fn=F.nll_loss)
+def test_finetuning(tmpdir, strategy, lr_scheduler, checker_class, checker_class_data):
+    task = TestTaskWithFinetuning(loss_fn=F.nll_loss, lr_scheduler=lr_scheduler, optimizer="sgd", learning_rate=0.1)
     callbacks = [] if checker_class is None else checker_class(dirpath=tmpdir, **checker_class_data)
     trainer = flash.Trainer(max_epochs=5, limit_train_batches=10, callbacks=callbacks)
     ds = DummyDataset()