improve finetuning

CHANGELOG.md

@@ -9,11 +9,16 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 
 ### Added
 
-- Added flash_notebook examples ([#9](https://github.com/PyTorchLightning/pytorch-lightning/pull/9))
+- Added flash_notebook examples ([#9](https://github.com/PyTorchLightning/lightning-flash/pull/9))
+
+
+- Added `strategy` to `trainer.finetune` with `NoFreeze`, `Freeze`, `FreezeUnfreeze`, `UnfreezeMilestones` Callbacks([#39](https://github.com/PyTorchLightning/lightning-flash/pull/39))
+
 
 ### Changed
 
+
 ### Fixed
 
 
-### Removed
+### Removed

README.md

@@ -127,7 +127,7 @@ model = ImageClassifier(num_classes=datamodule.num_classes)
 trainer = flash.Trainer(max_epochs=1)
 
 # 5. Finetune the model
-trainer.finetune(model, datamodule=datamodule, unfreeze_milestones=(0, 1))
+trainer.finetune(model, datamodule=datamodule, strategy="freeze")
 
 # 7. Save it!
 trainer.save_checkpoint("image_classification_model.pt")
@@ -151,13 +151,13 @@ Flash is built as a collection of community-built tasks. A task is highly opinio
 
 ### Example 1: Image classification
 Flash has an ImageClassification task to tackle any image classification problem.
-  
+
 <details>
   <summary>View example</summary>
   To illustrate, Let's say we wanted to develop a model that could classify between ants and bees.
-  
+
   <img src="https://pl-flash-data.s3.amazonaws.com/images/ant_bee.png" width="300px">
-  
+
   Here we classify ants vs bees.
 
   ```python
@@ -208,7 +208,7 @@ Flash has a TextClassification task to tackle any text classification problem.
 <details>
   <summary>View example</summary>
   To illustrate, say you wanted to classify movie reviews as positive or negative.
-  
+
   ```python
   import flash
   from flash import download_data
@@ -261,9 +261,9 @@ Flash has a TabularClassification task to tackle any tabular classification prob
 
 <details>
   <summary>View example</summary>
-  
-  To illustrate, say we want to build a model to predict if a passenger survived on the Titanic. 
-  
+
+  To illustrate, say we want to build a model to predict if a passenger survived on the Titanic.
+
   ```python
   from pytorch_lightning.metrics.classification import Accuracy, Precision, Recall
   import flash

flash/core/finetuning.py

@@ -0,0 +1,135 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from typing import List, Union
+
+import pytorch_lightning as pl
+from pytorch_lightning.callbacks import BaseFinetuning
+from pytorch_lightning.utilities import rank_zero_warn
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
+from torch import nn
+from torch.optim import Optimizer
+
+
+class FlashBaseFinetuning(BaseFinetuning):
+
+    def __init__(self, attr_names: Union[str, List[str]] = "backbone", train_bn: bool = True):
+        r"""
+
+        FlashBaseFinetuning can be used to create a custom Flash Finetuning Callback.
+
+        Override ``finetunning_function`` to put your unfreeze logic.
+
+        Args:
+            attr_names: Name(s) of the module attributes of the model to be frozen.
+
+            train_bn: Wether to train Batch Norm layer
+
+        """
+
+        self.attr_names = [attr_names] if isinstance(attr_names, str) else attr_names
+        self.train_bn = train_bn
+
+    def freeze_before_training(self, pl_module: pl.LightningModule) -> None:
+        self.freeze_using_attr_names(pl_module, self.attr_names, train_bn=self.train_bn)
+
+    def freeze_using_attr_names(self, pl_module, attr_names: List[str], train_bn: bool = True):
+        for attr_name in attr_names:
+            attr = getattr(pl_module, attr_name, None)
+            if attr is None or not isinstance(attr, nn.Module):
+                MisconfigurationException(f"Your model must have a {attr} attribute")
+            self.freeze(module=attr, train_bn=train_bn)
+
+
+class FreezeUnfreeze(FlashBaseFinetuning):
+
+    def __init__(self, attr_names: Union[str, List[str]] = "backbone", train_bn: bool = True, unfreeze_epoch: int = 10):
+        super().__init__(attr_names, train_bn)
+        self.unfreeze_epoch = unfreeze_epoch
+
+    def finetunning_function(
+        self,
+        pl_module: pl.LightningModule,
+        epoch: int,
+        optimizer: Optimizer,
+        opt_idx: int,
+    ) -> None:
+        if epoch == self.unfreeze_epoch:
+            modules = [getattr(pl_module, attr_name) for attr_name in self.attr_names]
+            self.unfreeze_and_add_param_group(
+                module=modules,
+                optimizer=optimizer,
+                train_bn=self.train_bn,
+            )
+
+
+class UnfreezeMilestones(FlashBaseFinetuning):
+
+    def __init__(
+        self,
+        attr_names: Union[str, List[str]] = "backbone",
+        train_bn: bool = True,
+        unfreeze_milestones: tuple = (5, 10),
+        num_layers: int = 5
+    ):
+        self.unfreeze_milestones = unfreeze_milestones
+        self.num_layers = num_layers
+
+        super().__init__(attr_names, train_bn)
+
+    def finetunning_function(
+        self,
+        pl_module: pl.LightningModule,
+        epoch: int,
+        optimizer: Optimizer,
+        opt_idx: int,
+    ) -> None:
+        backbone_modules = list(pl_module.backbone.modules())
+        if epoch == self.unfreeze_milestones[0]:
+            # unfreeze num_layers last layers
+            self.unfreeze_and_add_param_group(
+                module=backbone_modules[-self.num_layers:],
+                optimizer=optimizer,
+                train_bn=self.train_bn,
+            )
+
+        elif epoch == self.unfreeze_milestones[1]:
+            # unfreeze remaining layers
+            self.unfreeze_and_add_param_group(
+                module=backbone_modules[:-self.num_layers],
+                optimizer=optimizer,
+                train_bn=self.train_bn,
+            )
+
+
+_DEFAULTS_FINETUNE_STRATEGIES = {
+    "no_freeze": BaseFinetuning,
+    "freeze": FlashBaseFinetuning,
+    "freeze_unfreeze": FreezeUnfreeze,
+    "unfreeze_milestones": UnfreezeMilestones
+}
+
+
+def instantiate_default_finetuning_callbacks(strategy):
+    if strategy is None:
+        strategy = "no_freeze"
+        rank_zero_warn("strategy is None. Setting strategy to `no_freeze` by default.", UserWarning)
+    if isinstance(strategy, str):
+        strategy = strategy.lower()
+        if strategy in _DEFAULTS_FINETUNE_STRATEGIES:
+            return [_DEFAULTS_FINETUNE_STRATEGIES[strategy]()]
+        raise MisconfigurationException(
+            f"strategy should be within {list(_DEFAULTS_FINETUNE_STRATEGIES)}"
+            f". Found {strategy}"
+        )
+    return []

flash/core/model.py

@@ -150,3 +150,6 @@ def on_load_checkpoint(self, checkpoint: Dict[str, Any]) -> None:
 
     def on_save_checkpoint(self, checkpoint: Dict[str, Any]) -> None:
         checkpoint["pipeline"] = self.data_pipeline
+
+    def configure_finetune_callback(self):
+        return []

flash/core/trainer.py

@@ -16,54 +16,12 @@
 
 import pytorch_lightning as pl
 from pytorch_lightning.callbacks import BaseFinetuning
-from torch.optim import Optimizer
+from pytorch_lightning.core.lightning import LightningModule
+from pytorch_lightning.utilities import rank_zero_warn
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from torch.utils.data import DataLoader
 
-
-# NOTE: copied from:
-# https://github.com/PyTorchLightning/pytorch-lightning/blob/9d165f6f5655a44f1e5cd02ab36f21bc14e2a604/pl_examples/domain_templates/computer_vision_fine_tuning.py#L66
-class MilestonesFinetuningCallback(BaseFinetuning):
-
-    def __init__(self, milestones: tuple = (5, 10), train_bn: bool = True):
-        self.milestones = milestones
-        self.train_bn = train_bn
-
-    def freeze_before_training(self, pl_module: pl.LightningModule) -> None:
-        # TODO: might need some config to say which attribute is model
-        # maybe something like:
-        # self.freeze(module=pl_module.getattr(self.feature_attr), train_bn=self.train_bn)
-        # where self.feature_attr can be "backbone" or "feature_extractor", etc.
-        # (configured in init)
-        assert hasattr(
-            pl_module, "backbone"
-        ), "To use MilestonesFinetuningCallback your model must have a backbone attribute"
-        self.freeze(module=pl_module.backbone, train_bn=self.train_bn)
-
-    def finetunning_function(
-        self,
-        pl_module: pl.LightningModule,
-        epoch: int,
-        optimizer: Optimizer,
-        opt_idx: int,
-    ) -> None:
-        backbone_modules = list(pl_module.backbone.modules())
-        if epoch == self.milestones[0]:
-            # unfreeze 5 last layers
-            # TODO last N layers should be parameter
-            self.unfreeze_and_add_param_group(
-                module=backbone_modules[-5:],
-                optimizer=optimizer,
-                train_bn=self.train_bn,
-            )
-
-        elif epoch == self.milestones[1]:
-            # unfreeze remaining layers
-            # TODO last N layers should be parameter
-            self.unfreeze_and_add_param_group(
-                module=backbone_modules[:-5],
-                optimizer=optimizer,
-                train_bn=self.train_bn,
-            )
+from flash.core.finetuning import _DEFAULTS_FINETUNE_STRATEGIES, instantiate_default_finetuning_callbacks
 
 
 class Trainer(pl.Trainer):
@@ -96,13 +54,14 @@ def fit(
 
     def finetune(
         self,
-        model: pl.LightningModule,
+        model: LightningModule,
         train_dataloader: Optional[DataLoader] = None,
         val_dataloaders: Optional[Union[DataLoader, List[DataLoader]]] = None,
         datamodule: Optional[pl.LightningDataModule] = None,
-        unfreeze_milestones: tuple = (5, 10),
+        strategy: Optional[Union[str, BaseFinetuning]] = None,
     ):
         r"""
+
         Runs the full optimization routine. Same as pytorch_lightning.Trainer().fit(), but unfreezes layers
         of the backbone throughout training layers of the backbone throughout training.
 
@@ -117,18 +76,61 @@ def finetune(
             val_dataloaders: Either a single Pytorch Dataloader or a list of them, specifying validation samples.
                 If the model has a predefined val_dataloaders method this will be skipped
 
-            unfreeze_milestones: A tuple of two integers. First value marks the epoch in which the last 5
-            layers of the backbone will be unfrozen. The second value marks the epoch in which the full backbone will
-            be unfrozen.
+            strategy: Should either be a string or a finetuning callback subclassing
+                ``pytorch_lightning.callbacks.BaseFinetuning``.
 
-        """
-        if hasattr(model, "backbone"):
-            # TODO: if we find a finetuning callback in the trainer should we change it?
-            # or should we warn the user?
-            if not any(isinstance(c, BaseFinetuning) for c in self.callbacks):
-                # TODO: should pass config from arguments
-                self.callbacks.append(MilestonesFinetuningCallback(milestones=unfreeze_milestones))
-        else:
-            warnings.warn("Warning: model does not have a 'backbone' attribute, will train normally")
+                Currently, default strategies can be enabled with these strings:
+                    - ``no_freeze``,
+                    - ``freeze``,
+                    - ``freeze_unfreeze``,
+                    - ``unfreeze_milestones``
 
+        """
+        self._resolve_callbacks(model, strategy)
         return super().fit(model, train_dataloader, val_dataloaders, datamodule)
+
+    def _resolve_callbacks(self, model, strategy):
+        """
+        This function is used to select the `BaseFinetuning` to be used for finetuning.
+        """
+        if strategy is not None and not isinstance(strategy, (str, BaseFinetuning)):
+            raise MisconfigurationException(
+                "strategy should be a ``pytorch_lightning.callbacks.BaseFinetuning``"
+                f"callback or a str within {list(_DEFAULTS_FINETUNE_STRATEGIES.keys())}"
+            )
+
+        if isinstance(strategy, BaseFinetuning):
+            callback = strategy
+        else:
+            # todo: change to ``configure_callbacks`` when merged to Lightning.
+            model_callback = model.configure_finetune_callback()
+            if len(model_callback) > 1:
+                raise MisconfigurationException(
+                    f"{model} configure_finetune_callback should create a list with only 1 callback"
+                )
+            if len(model_callback) == 1:
+                if strategy is not None:
+                    rank_zero_warn(
+                        "The model contains a default finetune callback. "
+                        f"The provided {strategy} will be overriden. "
+                        "HINT: Provide a `BaseFinetuning` callback as strategy to make it prioritized. ", UserWarning
+                    )
+                callback = [model_callback]
+            else:
+                callback = instantiate_default_finetuning_callbacks(strategy)
+
+        self.callbacks = self._merge_callbacks(self.callbacks, [callback])
+
+    @staticmethod
+    def _merge_callbacks(old_callbacks: List, new_callbacks: List) -> List:
+        """
+        This function keeps only 1 instance of each callback type,
+        extending new_callbacks with old_callbacks
+        """
+        if len(new_callbacks):
+            return old_callbacks
+        new_callbacks_types = set(type(c) for c in new_callbacks)
+        old_callbacks_types = set(type(c) for c in old_callbacks)
+        override_types = new_callbacks_types.intersection(old_callbacks_types)
+        new_callbacks.extend(c for c in old_callbacks if type(c) not in override_types)
+        return new_callbacks

flash_examples/finetuning/image_classification.py

@@ -1,5 +1,6 @@
 import flash
 from flash.core.data import download_data
+from flash.core.finetuning import FreezeUnfreeze
 from flash.vision import ImageClassificationData, ImageClassifier
 
 if __name__ == "__main__":
@@ -17,11 +18,11 @@
     # 3. Build the model
     model = ImageClassifier(num_classes=datamodule.num_classes)
 
-    # 4. Create the trainer. Run once on data
-    trainer = flash.Trainer(max_epochs=1)
+    # 4. Create the trainer. Run twice on data
+    trainer = flash.Trainer(max_epochs=2)
 
     # 5. Train the model
-    trainer.finetune(model, datamodule=datamodule, unfreeze_milestones=(0, 1))
+    trainer.finetune(model, datamodule=datamodule, strategy=FreezeUnfreeze(unfreeze_epoch=1))
 
     # 6. Test the model
     trainer.test()

flash_examples/finetuning/text_classification.py

@@ -24,7 +24,7 @@
     trainer = flash.Trainer(max_epochs=1)
 
     # 5. Fine-tune the model
-    trainer.finetune(model, datamodule=datamodule, unfreeze_milestones=(0, 1))
+    trainer.finetune(model, datamodule=datamodule, strategy='freeze')
 
     # 6. Test model
     trainer.test()