Simplify Lightning task and model creation

Summary:
Given that the way to create D2 (https://github.com/facebookresearch/d2go/commit/465cdb842513eb910aa20fcedea1d2edd15dc7b7)go runner and Lightning task are different, get_class was introduced so that in application we could do:
```
if is Lightning:
    task_cls = get_class(classname)
    task = task_cls(cfg)
else:
    runner = create_runner(classname)
```
It turns out that we could need to do that in many places: workflow, binaries.
This diff revert `get_class` and return class in `create_runner` if the class is a Lightning module.

Reviewed By: newstzpz

Differential Revision: D26676595

fbshipit-source-id: c3ce2016d09fe073af4c2dd9f98eea4e59ca621b

d2go/runner/__init__.py

@@ -3,19 +3,24 @@
 
 
 import importlib
-from typing import Type
+from typing import Type, Union
+
+from pytorch_lightning import LightningModule
 
 from .default_runner import BaseRunner, Detectron2GoRunner, GeneralizedRCNNRunner
 
-def get_class(class_full_name: str) -> Type:
-    """Imports and returns the task class."""
+
+def create_runner(
+    class_full_name: str, *args, **kwargs
+) -> Union[BaseRunner, Type[LightningModule]]:
+    """Constructs a runner instance if class is a d2go runner. Returns class
+        type if class is a Lightning module.
+    """
     runner_module_name, runner_class_name = class_full_name.rsplit(".", 1)
     runner_module = importlib.import_module(runner_module_name)
     runner_class = getattr(runner_module, runner_class_name)
+    if issubclass(runner_class, LightningModule):
+        # Return runner class for Lightning module since it requires config
+        # to construct
         return runner_class
-
-
-def create_runner(class_full_name: str, *args, **kwargs) -> BaseRunner:
-    """Constructs a runner instance of the given class."""
-    runner_class = get_class(class_full_name)
     return runner_class(*args, **kwargs)

d2go/runner/lightning_task.py

 #!/usr/bin/env python3
 # Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
 
+import logging
 import os
 from copy import deepcopy
 from enum import Enum
@@ -9,6 +10,14 @@ from typing import Any, Dict, List, Optional, Tuple
 import pytorch_lightning as pl
 import torch
 from d2go.config import CfgNode
+from d2go.data.datasets import inject_coco_datasets, register_dynamic_datasets
+from d2go.data.utils import (
+    update_cfg_if_using_adhoc_dataset,
+)
+from d2go.export.d2_meta_arch import patch_d2_meta_arch
+from d2go.modeling.model_freezing_utils import (
+    set_requires_grad,
+)
 from d2go.runner.default_runner import (
     Detectron2GoRunner,
     GeneralizedRCNNRunner,
@@ -25,6 +34,9 @@ from pytorch_lightning.utilities import rank_zero_info
 _STATE_DICT_KEY = "state_dict"
 _OLD_STATE_DICT_KEY = "model"
 
+logging.basicConfig(level=logging.INFO)
+logger = logging.getLogger(__name__)
+
 
 def _is_lightning_checkpoint(checkpoint: Dict[str, Any]) -> bool:
     """ Returns true if we believe this checkpoint to be a Lightning checkpoint. """
@@ -73,8 +85,9 @@ class ModelTag(str, Enum):
 class DefaultTask(pl.LightningModule):
     def __init__(self, cfg: CfgNode):
         super().__init__()
+        self.register(cfg)
         self.cfg = cfg
-        self.model = build_model(cfg)
+        self.model = self._build_model()
         self.storage = None
         # evaluators for validation datasets, split by model tag(default, ema),
         # in the order of DATASETS.TEST
@@ -94,6 +107,64 @@ class DefaultTask(pl.LightningModule):
     def setup(self, stage: str):
         setup_after_launch(self.cfg, self.cfg.OUTPUT_DIR, runner=None)
 
+    def register(self, cfg: CfgNode):
+        inject_coco_datasets(cfg)
+        register_dynamic_datasets(cfg)
+        update_cfg_if_using_adhoc_dataset(cfg)
+        patch_d2_meta_arch()
+
+    def _build_model(self):
+        model = build_model(self.cfg)
+
+        if self.cfg.MODEL.FROZEN_LAYER_REG_EXP:
+            set_requires_grad(model, self.cfg.MODEL.FROZEN_LAYER_REG_EXP, value=False)
+
+        return model
+
+    @classmethod
+    def from_config(cls, cfg: CfgNode, eval_only=False):
+        """Builds Lightning module including model from config.
+        To load weights from a pretrained checkpoint, please specify checkpoint
+        path in `MODEL.WEIGHTS`.
+
+        Args:
+            cfg: D2go config node.
+            eval_only: True if module should be in eval mode.
+        """
+        if eval_only and not cfg.MODEL.WEIGHTS:
+            logger.warning("MODEL.WEIGHTS is missing for eval only mode.")
+
+        if cfg.MODEL.WEIGHTS:
+            # only load model weights from checkpoint
+            logger.info(f"Load model weights from checkpoint: {cfg.MODEL.WEIGHTS}.")
+            task = cls.load_from_checkpoint(cfg.MODEL.WEIGHTS, cfg=cfg)
+        else:
+            task = cls(cfg)
+
+        if cfg.MODEL_EMA.ENABLED and cfg.MODEL_EMA.USE_EMA_WEIGHTS_FOR_EVAL_ONLY:
+            assert task.ema_state, "EMA state is not loaded from checkpoint."
+            task.ema_state.apply_to(task.model)
+
+        if eval_only:
+            task.eval()
+        return task
+
+    @classmethod
+    def build_model(cls, cfg: CfgNode, eval_only=False):
+        """Builds D2go model instance from config.
+        NOTE: For backward compatible with existing D2Go tools. Prefer
+        `from_config` in other use cases.
+
+        Args:
+            cfg: D2go config node.
+            eval_only: True if model should be in eval mode.
+        """
+        return cls.from_config(cfg, eval_only).model
+
+    @classmethod
+    def get_default_cfg(cls):
+        return Detectron2GoRunner.get_default_cfg()
+
     @classmethod
     def get_default_cfg(cls):
         return Detectron2GoRunner.get_default_cfg()
@@ -224,6 +295,13 @@ class DefaultTask(pl.LightningModule):
     def forward(self, input):
         return self.model(input)
 
+    @staticmethod
+    def _initialize(cfg: CfgNode):
+        pass
+
+    # ---------------------------------------------------------------------------
+    # Hooks
+    # ---------------------------------------------------------------------------
     def on_pretrain_routine_end(self) -> None:
         if self.cfg.MODEL_EMA.ENABLED:
             if self.ema_state and self.ema_state.has_inited():

tests/test_runner_default_runner.py

@@ -9,6 +9,7 @@ import unittest
 
 import d2go.runner.default_runner as default_runner
 import torch
+from d2go.runner import create_runner
 from d2go.utils.testing import helper
 from d2go.utils.testing.data_loader_helper import create_local_dataset
 from detectron2.evaluation import COCOEvaluator, RotatedCOCOEvaluator
@@ -160,6 +161,17 @@ class TestDefaultRunner(unittest.TestCase):
                 ds_evaluators = runner.get_evaluator(cfg, ds_name, tmp_dir)
                 self.assertTrue(isinstance(ds_evaluators._evaluators[0], evaluator))
 
+    def test_create_runner(self):
+        runner = create_runner(
+            ".".join(
+                [
+                    default_runner.Detectron2GoRunner.__module__,
+                    default_runner.Detectron2GoRunner.__name__,
+                ]
+            )
+        )
+        self.assertTrue(isinstance(runner, default_runner.Detectron2GoRunner))
+
     @helper.enable_ddp_env
     def test_d2go_runner_ema(self):
         with tempfile.TemporaryDirectory() as tmp_dir:

tests/test_runner_lightning_task.py

@@ -3,16 +3,17 @@
 
 
 import os
-import tempfile
 import unittest
 from copy import deepcopy
 from typing import Dict
 
 import pytorch_lightning as pl  # type: ignore
 import torch
-from d2go.config import CfgNode
+from d2go.config import CfgNode, temp_defrost
+from d2go.runner import create_runner
 from d2go.runner.lightning_task import GeneralizedRCNNTask
 from d2go.utils.testing import meta_arch_helper as mah
+from d2go.utils.testing.helper import tempdir
 from detectron2.utils.events import EventStorage
 from pytorch_lightning.callbacks.model_checkpoint import ModelCheckpoint
 from torch import Tensor
@@ -35,8 +36,8 @@ class TestLightningTask(unittest.TestCase):
                 return False
         return True
 
-    def test_load_from_checkpoint(self) -> None:
-        with tempfile.TemporaryDirectory() as tmp_dir:
+    @tempdir
+    def test_load_from_checkpoint(self, tmp_dir) -> None:
         task = GeneralizedRCNNTask(self._get_cfg(tmp_dir))
 
         checkpoint_callback = ModelCheckpoint(dirpath=task.cfg.OUTPUT_DIR)
@@ -44,7 +45,7 @@ class TestLightningTask(unittest.TestCase):
             "max_steps": 1,
             "limit_train_batches": 1,
             "num_sanity_val_steps": 0,
-                "callbacks": [checkpoint_callback],
+            "checkpoint_callback": checkpoint_callback,
         }
         trainer = pl.Trainer(**params)
         with EventStorage() as storage:
@@ -62,8 +63,8 @@ class TestLightningTask(unittest.TestCase):
                 )
             )
 
-    def test_train_ema(self):
-        with tempfile.TemporaryDirectory() as tmp_dir:
+    @tempdir
+    def test_train_ema(self, tmp_dir):
         cfg = self._get_cfg(tmp_dir)
         cfg.MODEL_EMA.ENABLED = True
         cfg.MODEL_EMA.DECAY = 0.7
@@ -86,8 +87,8 @@ class TestLightningTask(unittest.TestCase):
             self._compare_state_dict(init_state, task.ema_state.state_dict())
         )
 
-    def test_load_ema_weights(self):
-        with tempfile.TemporaryDirectory() as tmp_dir:
+    @tempdir
+    def test_load_ema_weights(self, tmp_dir):
         cfg = self._get_cfg(tmp_dir)
         cfg.MODEL_EMA.ENABLED = True
         task = GeneralizedRCNNTask(cfg)
@@ -123,3 +124,54 @@ class TestLightningTask(unittest.TestCase):
                 task.ema_state.state_dict(), task2.model.state_dict()
             )
         )
+
+    def test_create_runner(self):
+        task_cls = create_runner(
+            f"{GeneralizedRCNNTask.__module__}.{GeneralizedRCNNTask.__name__}"
+        )
+        self.assertTrue(task_cls == GeneralizedRCNNTask)
+
+    @tempdir
+    def test_build_model(self, tmp_dir):
+        cfg = self._get_cfg(tmp_dir)
+        cfg.MODEL_EMA.ENABLED = True
+        task = GeneralizedRCNNTask(cfg)
+        checkpoint_callback = ModelCheckpoint(
+            dirpath=task.cfg.OUTPUT_DIR, save_last=True
+        )
+
+        trainer = pl.Trainer(
+            max_steps=1,
+            limit_train_batches=1,
+            num_sanity_val_steps=0,
+            callbacks=[checkpoint_callback],
+        )
+
+        with EventStorage() as storage:
+            task.storage = storage
+            trainer.fit(task)
+
+        # test building untrained model
+        model = GeneralizedRCNNTask.build_model(cfg)
+        self.assertTrue(model.training)
+
+        # test loading regular weights
+        with temp_defrost(cfg):
+            cfg.MODEL.WEIGHTS = os.path.join(tmp_dir, "last.ckpt")
+            model = GeneralizedRCNNTask.build_model(cfg, eval_only=True)
+            self.assertFalse(model.training)
+            self.assertTrue(
+                self._compare_state_dict(model.state_dict(), task.model.state_dict())
+            )
+
+        # test loading EMA weights
+        with temp_defrost(cfg):
+            cfg.MODEL.WEIGHTS = os.path.join(tmp_dir, "last.ckpt")
+            cfg.MODEL_EMA.USE_EMA_WEIGHTS_FOR_EVAL_ONLY = True
+            model = GeneralizedRCNNTask.build_model(cfg, eval_only=True)
+            self.assertFalse(model.training)
+            self.assertTrue(
+                self._compare_state_dict(
+                    model.state_dict(), task.ema_state.state_dict()
+                )
+            )

tools/lightning_train_net.py

@@ -9,7 +9,7 @@ from typing import Any, Dict, List, Optional, Type
 
 import pytorch_lightning as pl  # type: ignore
 from d2go.config import CfgNode, temp_defrost
-from d2go.runner import get_class
+from d2go.runner import create_runner
 from d2go.runner.callbacks.quantization import QuantizationAwareTraining
 from d2go.runner.lightning_task import GeneralizedRCNNTask
 from d2go.setup import basic_argument_parser
@@ -80,26 +80,6 @@ def _get_trainer_callbacks(cfg: CfgNode) -> List[Callback]:
     return callbacks
 
 
-def build_task(
-    cfg: CfgNode, task_cls: Type[GeneralizedRCNNTask]
-) -> GeneralizedRCNNTask:
-    """Builds instance of Lightning module based on the config and task class
-       name. To build a pre-trained model, specify the `MODEL.WEIGHTS` in the
-       config.
-
-    Args:
-        cfg: The normalized ConfigNode for this D2Go Task.
-        task_cls: Lightning module class name.
-
-    Returns:
-        A instance of the given Lightning module.
-    """
-    if cfg.MODEL.WEIGHTS:
-        # only load model weights from checkpoint
-        logger.info(f"Load model weights from checkpoint: {cfg.MODEL.WEIGHTS}.")
-        return task_cls.load_from_checkpoint(cfg.MODEL.WEIGHTS, cfg=cfg)
-    return task_cls(cfg)
-
 
 def do_train(cfg: CfgNode, trainer: pl.Trainer, task: GeneralizedRCNNTask) -> Dict[str, str]:
     """Runs the training loop with given trainer and task.
@@ -169,7 +149,7 @@ def main(
 
     maybe_override_output_dir(cfg, output_dir)
 
-    task = build_task(cfg, task_cls)
+    task = task_cls.from_config(cfg, eval_only)
     tb_logger = TensorBoardLogger(save_dir=cfg.OUTPUT_DIR)
     trainer_params = {
         # training loop is bounded by max steps, use a large max_epochs to make
@@ -239,7 +219,7 @@ def argument_parser():
 
 if __name__ == "__main__":
     args = argument_parser().parse_args()
-    task_cls = get_class(args.runner) if args.runner else GeneralizedRCNNTask
+    task_cls = create_runner(args.runner) if args.runner else GeneralizedRCNNTask
     cfg = build_config(args.config_file, task_cls, args.opts)
     ret = main(
         cfg,