# Copyright The Lightning AI 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. import os from copy import deepcopy from dataclasses import dataclass from typing import Dict, Iterator from unittest.mock import ANY, Mock import pytest import torch from torch.utils.data.dataloader import _MultiProcessingDataLoaderIter, DataLoader from lightning.pytorch import LightningModule, Trainer from lightning.pytorch.callbacks import Callback, ModelCheckpoint, OnExceptionCheckpoint from lightning.pytorch.demos.boring_classes import BoringModel, RandomDataset from lightning.pytorch.loops import _Loop from lightning.pytorch.loops.progress import BaseProgress def test_restarting_loops_recursive(): class MyLoop(_Loop): def __init__(self, loop=None): super().__init__(Mock()) self.child = loop loop = MyLoop(MyLoop(MyLoop())) assert not loop.restarting assert not loop.child.restarting assert not loop.child.child.restarting loop.restarting = True assert loop.restarting assert loop.child.restarting assert loop.child.child.restarting class CustomException(Exception): pass def test_loop_restore(): class Simple(_Loop): def __init__(self, trainer, dataset: Iterator): super().__init__(trainer) self.iteration_count = 0 self.dataset = dataset def run(self): self.reset() while not self.iteration_count > len(self.dataset): try: self.advance() self.iteration_count += 1 self._restarting = False except StopIteration: break self._restarting = False def reset(self) -> None: self.iter_dataset = iter(self.dataset) if self.restarting: for _ in range(self.iteration_count): next(self.iter_dataset) self.iteration_count += 1 else: self.outputs = [] def advance(self) -> None: value = next(self.iter_dataset) if self.iteration_count == 5: raise CustomException self.outputs.append(value) def state_dict(self) -> Dict: return {"iteration_count": self.iteration_count, "outputs": self.outputs} def load_state_dict(self, state_dict: Dict) -> None: self.iteration_count = state_dict["iteration_count"] self.outputs = state_dict["outputs"] trainer = Trainer() data = range(10) loop = Simple(trainer, data) try: loop.run() state_dict = {} except CustomException: state_dict = loop.state_dict() loop = Simple(trainer, data) loop.load_state_dict(state_dict) loop.restarting = True loop.run() assert not loop.restarting assert loop.outputs == list(range(10)) def test_loop_hierarchy(): @dataclass class SimpleProgress(BaseProgress): increment: int = 0 class Simple(_Loop): def __init__(self, trainer, a): super().__init__(trainer) self.a = a self.progress = SimpleProgress() def run(self): while not self.progress.increment > 0: try: self.advance() self.progress.increment += 1 self._restarting = False except StopIteration: break self._restarting = False def advance(self) -> None: loop = getattr(self, "loop_child", None) if not loop: return loop.run() def on_save_checkpoint(self) -> Dict: return {"a": self.a} def on_load_checkpoint(self, state_dict: Dict) -> None: self.a = state_dict["a"] trainer = Trainer() loop_parent = Simple(trainer, 1) loop_child = Simple(trainer, 2) loop_parent.loop_child = loop_child state_dict = loop_parent.state_dict() assert state_dict == { "state_dict": {"a": 1}, "progress": {"increment": 0}, "loop_child.state_dict": {"a": 2}, "loop_child.progress": {"increment": 0}, } state_dict["loop_child.state_dict"]["a"] = 3 # check restarting after `load_state_dict` loop_parent.load_state_dict(state_dict) assert loop_parent.restarting loop_parent.run() # check the new state after `run` state_dict = loop_parent.state_dict() assert state_dict == { "state_dict": {"a": 1}, "progress": {"increment": 1}, "loop_child.state_dict": {"a": 3}, "loop_child.progress": {"increment": 1}, } loop_parent_copy = deepcopy(loop_parent) assert loop_parent_copy.state_dict() == loop_parent.state_dict() assert loop_parent_copy.on_save_checkpoint() == state_dict["state_dict"] assert loop_parent_copy.loop_child.on_save_checkpoint() == state_dict["loop_child.state_dict"] loop_parent = Simple(trainer, 1) loop_child = Simple(trainer, 2) loop_parent.loop_child = loop_child loop_parent.load_state_dict(state_dict) assert loop_parent.progress.increment == 1 assert loop_parent.loop_child.progress.increment == 1 del loop_parent.loop_child state_dict = loop_parent.state_dict() assert state_dict == {"state_dict": {"a": 1}, "progress": {"increment": 1}} @pytest.mark.parametrize("stop_epoch", (1, 2)) @pytest.mark.parametrize("stop_batch", (1, 2)) @pytest.mark.parametrize("n_dataloaders,stop_dataloader", [(2, 0), (2, 1), (3, 2)]) def test_loop_restart_progress_multiple_dataloaders(tmpdir, n_dataloaders, stop_dataloader, stop_epoch, stop_batch): n_batches = 5 n_epochs = 3 class ValidationModel(BoringModel): def __init__(self): super().__init__() def validation_step(self, batch, batch_idx, dataloader_idx): if self.current_epoch == stop_epoch and batch_idx == stop_batch and dataloader_idx == stop_dataloader: raise CustomException return super().validation_step(batch, batch_idx) def val_dataloader(self): return [super(ValidationModel, self).val_dataloader() for _ in range(n_dataloaders)] model = ValidationModel() trainer = Trainer( default_root_dir=tmpdir, max_epochs=n_epochs, limit_train_batches=1, limit_val_batches=n_batches, callbacks=OnExceptionCheckpoint(tmpdir), ) # simulate a failure with pytest.raises(CustomException): trainer.fit(model) ckpt_path = str(tmpdir / "on_exception.ckpt") checkpoint = torch.load(ckpt_path)["loops"]["fit_loop"] trainer.fit_loop.load_state_dict(checkpoint) # `nbe_`: non-breaking epoch, as in, no exception will be raised. `be_`: breaking epoch # the fit-validation total batch progress is reset per epoch so it's not counted for the total value. nbe_total_val_batch = 0 # stop_epoch * n_dataloaders * n_batches be_total_val_batch = stop_dataloader * n_batches + stop_batch total_val_batch = nbe_total_val_batch + be_total_val_batch expected = { "total": { "ready": total_val_batch + 1, "started": total_val_batch + 1, "processed": total_val_batch, "completed": total_val_batch, }, "current": { "ready": total_val_batch + 1, "started": total_val_batch + 1, "processed": total_val_batch, "completed": total_val_batch, }, "is_last_batch": False, } assert trainer.fit_loop.epoch_loop.val_loop.batch_progress.state_dict() == expected @pytest.mark.parametrize("accumulate_grad_batches", (1, 2, 3)) @pytest.mark.parametrize("stop_epoch", (1, 2)) @pytest.mark.parametrize("stop_batch", (1, 2)) def test_loop_state_on_exception(accumulate_grad_batches, stop_epoch, stop_batch, tmpdir): n_epochs = 3 n_batches = 3 class TestModel(BoringModel): def training_step(self, batch, batch_idx): if self.trainer.current_epoch == stop_epoch and batch_idx == stop_batch: raise CustomException return super().training_step(batch, batch_idx) model = TestModel() trainer = Trainer( default_root_dir=tmpdir, max_epochs=n_epochs, limit_train_batches=n_batches, limit_val_batches=0, accumulate_grad_batches=accumulate_grad_batches, enable_progress_bar=False, logger=False, callbacks=OnExceptionCheckpoint(tmpdir), ) # simulate a failure with pytest.raises(CustomException): trainer.fit(model) ckpt_path = str(tmpdir / "on_exception.ckpt") assert os.path.exists(ckpt_path) checkpoint = torch.load(ckpt_path) optim_progress = trainer.fit_loop.epoch_loop.automatic_optimization.optim_progress sch_progress = trainer.fit_loop.epoch_loop.scheduler_progress # `nbe_`: non-breaking epoch, as in, no exception will be raised. `be_`: breaking epoch nbe_batches_completed = stop_epoch * n_batches be_batches_completed = stop_batch # lightning applies leftover accumulated gradients when the epoch ends has_leftover_accumulation_batches = n_batches % accumulate_grad_batches != 0 # number of batches that will call `optimizer.step()` during non-breaking and breaking epochs nbe_stepping_batches = nbe_batches_completed // accumulate_grad_batches be_stepping_batches = be_batches_completed // accumulate_grad_batches nbe_total_opt_steps = nbe_stepping_batches + has_leftover_accumulation_batches be_total_opt_steps = be_stepping_batches assert optim_progress.optimizer_steps == nbe_total_opt_steps + be_total_opt_steps assert optim_progress.optimizer.step.current.completed == be_total_opt_steps has_opt_stepped_in_be = stop_batch + 1 >= accumulate_grad_batches nbe_total_zero_grad = nbe_stepping_batches + has_leftover_accumulation_batches # `max` because the first batch always zero-grads be_total_zero_grad = max(1, be_stepping_batches) assert optim_progress.optimizer.zero_grad.total.completed == nbe_total_zero_grad + be_total_zero_grad assert optim_progress.optimizer.zero_grad.current.completed == be_total_zero_grad nbe_sch_steps = stop_epoch be_sch_steps = 0 # the current epoch did not complete assert sch_progress.total.completed == nbe_sch_steps + be_sch_steps assert sch_progress.current.completed == be_sch_steps expected = { "state_dict": ANY, "epoch_progress": { "total": { "ready": stop_epoch + 1, "started": stop_epoch + 1, "processed": stop_epoch, "completed": stop_epoch, }, "current": { "ready": stop_epoch + 1, "started": stop_epoch + 1, "processed": stop_epoch, "completed": stop_epoch, }, }, "epoch_loop.state_dict": ANY, "epoch_loop.batch_progress": { "total": { "ready": nbe_batches_completed + be_batches_completed + 1, "started": nbe_batches_completed + be_batches_completed + 1, "processed": nbe_batches_completed + be_batches_completed, "completed": nbe_batches_completed + be_batches_completed, }, "current": { "ready": stop_batch + 1, "started": stop_batch + 1, "processed": stop_batch, "completed": stop_batch, }, "is_last_batch": False, }, "epoch_loop.scheduler_progress": { "total": {"ready": nbe_sch_steps + be_sch_steps, "completed": nbe_sch_steps + be_sch_steps}, "current": {"ready": be_sch_steps, "completed": be_sch_steps}, }, "epoch_loop.manual_optimization.state_dict": ANY, "epoch_loop.manual_optimization.optim_step_progress": { "total": {"ready": 0, "completed": 0}, "current": {"ready": 0, "completed": 0}, }, "epoch_loop.automatic_optimization.state_dict": {}, "epoch_loop.automatic_optimization.optim_progress": { "optimizer": { "step": { "total": { "ready": nbe_total_opt_steps + be_total_opt_steps + has_opt_stepped_in_be, "completed": nbe_total_opt_steps + be_total_opt_steps, }, "current": {"ready": be_total_opt_steps + has_opt_stepped_in_be, "completed": be_total_opt_steps}, }, "zero_grad": { "total": { "ready": nbe_total_zero_grad + be_total_zero_grad, "started": nbe_total_zero_grad + be_total_zero_grad, "completed": nbe_total_zero_grad + be_total_zero_grad, }, "current": { "ready": be_total_zero_grad, "started": be_total_zero_grad, "completed": be_total_zero_grad, }, }, }, }, "epoch_loop.val_loop.state_dict": ANY, "epoch_loop.val_loop.batch_progress": ANY, } assert checkpoint["loops"]["fit_loop"] == expected trainer.fit_loop.load_state_dict(checkpoint["loops"]["fit_loop"]) state_dict = trainer.fit_loop.state_dict() # need to remove these elements for comparison; comparing with `fit_loop.state_dict()` would require the # fit loop to have an iterator, which is only available during training state_dict["epoch_loop.state_dict"]["dataloader_state_dict"] = ANY checkpoint["loops"]["fit_loop"]["epoch_loop.state_dict"]["dataloader_state_dict"] = ANY assert state_dict == checkpoint["loops"]["fit_loop"] trainer.fit_loop.load_state_dict(checkpoint["loops"]["fit_loop"]) # test resetting manually, we expect all `ready` counters to be reset to `completed` trainer.fit_loop.reset() trainer.fit_loop.epoch_loop.reset() epoch_progress = trainer.fit_loop.epoch_progress assert epoch_progress.current.ready == stop_epoch assert epoch_progress.current.completed == stop_epoch batch_progress = trainer.fit_loop.epoch_loop.batch_progress assert batch_progress.current.ready == be_batches_completed assert batch_progress.current.completed == be_batches_completed optim_progress = trainer.fit_loop.epoch_loop.automatic_optimization.optim_progress assert optim_progress.optimizer.step.current.ready == be_total_opt_steps assert optim_progress.optimizer.step.current.completed == be_total_opt_steps assert optim_progress.optimizer.zero_grad.current.ready == be_total_zero_grad assert optim_progress.optimizer.zero_grad.current.completed == be_total_zero_grad state_dict = trainer.fit_loop.state_dict() assert state_dict != checkpoint["loops"]["fit_loop"] assert state_dict["epoch_progress"]["total"]["started"] == stop_epoch + 1 assert state_dict["epoch_progress"]["current"]["started"] == stop_epoch def test_loop_state_on_complete_run(tmpdir): n_epochs = 3 n_batches = 3 accumulate_grad_batches = 1 class TestModel(BoringModel): def train_dataloader(self): # override to test the `is_last_batch` value return DataLoader(RandomDataset(32, n_batches)) model = TestModel() trainer = Trainer( default_root_dir=tmpdir, max_epochs=n_epochs, limit_val_batches=0, accumulate_grad_batches=accumulate_grad_batches, enable_progress_bar=False, logger=False, ) trainer.fit(model) assert trainer.num_training_batches == n_batches ckpt_path = trainer.checkpoint_callback.best_model_path assert os.path.exists(ckpt_path) checkpoint = torch.load(ckpt_path) n_sch_steps_total = n_epochs n_sch_steps_current = 1 expected = { "state_dict": ANY, "epoch_progress": { "total": { "ready": n_epochs, "started": n_epochs, "processed": n_epochs, "completed": n_epochs - 1, }, "current": { "ready": n_epochs, "started": n_epochs, "processed": n_epochs, "completed": n_epochs - 1, }, }, "epoch_loop.state_dict": ANY, "epoch_loop.batch_progress": { "total": { "ready": n_epochs * n_batches, "started": n_epochs * n_batches, "processed": n_epochs * n_batches, "completed": n_epochs * n_batches, }, "current": { "ready": n_batches, "started": n_batches, "processed": n_batches, "completed": n_batches, }, "is_last_batch": True, }, "epoch_loop.scheduler_progress": { "total": {"ready": n_sch_steps_total, "completed": n_sch_steps_total}, "current": {"ready": n_sch_steps_current, "completed": n_sch_steps_current}, }, "epoch_loop.manual_optimization.state_dict": ANY, "epoch_loop.manual_optimization.optim_step_progress": { "total": {"ready": 0, "completed": 0}, "current": {"ready": 0, "completed": 0}, }, "epoch_loop.automatic_optimization.state_dict": {}, "epoch_loop.automatic_optimization.optim_progress": { "optimizer": { "step": { "total": { "ready": n_epochs * n_batches, "completed": n_epochs * n_batches, }, "current": { "ready": n_batches, "completed": n_batches, }, }, "zero_grad": { "total": { "ready": n_epochs * n_batches, "started": n_epochs * n_batches, "completed": n_epochs * n_batches, }, "current": { "ready": n_batches, "started": n_batches, "completed": n_batches, }, }, }, }, "epoch_loop.val_loop.state_dict": ANY, "epoch_loop.val_loop.batch_progress": ANY, } assert checkpoint["loops"]["fit_loop"] == expected def test_fit_loop_reset(tmpdir): """Test that the reset logic in fit- and epoch loop is aware of whether the loop is restarting from a completed loop or from a mid-epoch checkpoint.""" # generate checkpoints at end of epoch and mid-epoch model = BoringModel() checkpoint_callback = ModelCheckpoint( dirpath=tmpdir, every_n_train_steps=2, save_top_k=-1, ) trainer = Trainer( default_root_dir=tmpdir, limit_train_batches=4, max_epochs=2, callbacks=[checkpoint_callback], logger=False, enable_model_summary=False, ) trainer.fit(model) # reset state loaded from a checkpoint from mid-epoch mid_epoch_ckpt = torch.load(str(tmpdir / "epoch=0-step=2.ckpt")) fit_loop = trainer.fit_loop epoch_loop = fit_loop.epoch_loop optimizer_loop = epoch_loop.automatic_optimization assert not fit_loop.restarting assert not epoch_loop.restarting assert not optimizer_loop.restarting # we load exactly what was saved - no reset yet fit_loop.load_state_dict(mid_epoch_ckpt["loops"]["fit_loop"]) # resetting from a mid-of-epoch checkpoint SHOULD NOT reset the current counters to 0 fit_loop.reset() epoch_loop.reset() assert fit_loop.restarting assert fit_loop.epoch_progress.total.ready == 1 assert fit_loop.epoch_progress.total.completed == 0 # the checkpoint was saved mid epoch assert fit_loop.epoch_progress.current.ready == 0 assert fit_loop.epoch_progress.current.completed == 0 assert epoch_loop.restarting assert epoch_loop.batch_progress.total.ready == 2 assert epoch_loop.batch_progress.total.processed == 2 assert epoch_loop.batch_progress.total.completed == 1 # the checkpoint was saved on train_batch_end assert epoch_loop.batch_progress.current.ready == 1 # currents get set to the completed value assert epoch_loop.batch_progress.current.processed == 1 assert epoch_loop.batch_progress.current.completed == 1 assert optimizer_loop.restarting # reset state loaded from a checkpoint from the end of an epoch end_of_epoch_ckpt = torch.load(str(tmpdir / "epoch=0-step=4.ckpt")) fit_loop = trainer.fit_loop epoch_loop = fit_loop.epoch_loop fit_loop.restarting = False epoch_loop.restarting = False optimizer_loop.restarting = False # we load exactly what was saved - no reset yet fit_loop.load_state_dict(end_of_epoch_ckpt["loops"]["fit_loop"]) # resetting from a end-of-epoch checkpoint SHOULD reset the current counters to 0 fit_loop.reset() epoch_loop.reset() assert fit_loop.restarting assert fit_loop.epoch_progress.total.ready == 1 assert fit_loop.epoch_progress.total.completed == 0 # the checkpoint saves before the epoch completes assert fit_loop.epoch_progress.current.ready == 0 assert fit_loop.epoch_progress.current.completed == 0 assert epoch_loop.restarting assert epoch_loop.batch_progress.total.ready == 4 assert epoch_loop.batch_progress.total.processed == 4 assert epoch_loop.batch_progress.total.completed == 3 # the checkpoint was saved on train_batch_end assert epoch_loop.batch_progress.current.ready == 3 # currents get set to the completed value assert epoch_loop.batch_progress.current.processed == 3 assert epoch_loop.batch_progress.current.completed == 3 @pytest.mark.parametrize( ["train_datasets", "val_datasets"], [([RandomDataset], [RandomDataset]), ([RandomDataset], [RandomDataset, RandomDataset])], ) @pytest.mark.parametrize("val_check_interval", [0.5, 1.0]) def test_fit_can_fail_during_validation(train_datasets, val_datasets, val_check_interval, tmpdir): size, n_batches = 2, 4 stop_batch = 1 n_val_dataloaders = len(val_datasets) stop_dataloader = n_val_dataloaders - 1 class TestModel(LightningModule): def __init__(self, should_fail): super().__init__() self.layer = torch.nn.Linear(size, 2) self.should_fail = should_fail def step(self, batch): return sum(self.layer(b).sum() for b in batch) def training_step(self, batch, batch_idx): return self.step(batch) def validation_step(self, batch, batch_idx, dataloader_idx=0): if self.should_fail and dataloader_idx == stop_dataloader and batch_idx == stop_batch: raise CustomException return self.step(batch) def configure_optimizers(self): return torch.optim.SGD(self.layer.parameters(), lr=0.1) def train_dataloader(self): return [DataLoader(cls(size, n_batches)) for cls in train_datasets] def val_dataloader(self): return [DataLoader(cls(size, n_batches)) for cls in val_datasets] model = TestModel(False) trainer = Trainer( default_root_dir=tmpdir, max_epochs=1, val_check_interval=val_check_interval, num_sanity_val_steps=0, enable_progress_bar=False, callbacks=OnExceptionCheckpoint(tmpdir), ) trainer.fit(model) ckpt_path = os.path.join(tmpdir, "on_exception.ckpt") assert not os.path.exists(ckpt_path), "Shouldn't have failed" state_dict = trainer.fit_loop.state_dict() expected_global_step = trainer.global_step assert state_dict["epoch_loop.batch_progress"] == { "total": {"ready": n_batches, "started": n_batches, "processed": n_batches, "completed": n_batches}, "current": {"ready": n_batches, "started": n_batches, "processed": n_batches, "completed": n_batches}, "is_last_batch": True, } val_per_epoch = int(1 // val_check_interval) assert state_dict["epoch_loop.val_loop.batch_progress"] == { "total": { "ready": n_val_dataloaders * val_per_epoch * n_batches, "started": n_val_dataloaders * val_per_epoch * n_batches, "processed": n_val_dataloaders * val_per_epoch * n_batches, "completed": n_val_dataloaders * val_per_epoch * n_batches, }, "current": { "ready": n_val_dataloaders * n_batches, "started": n_val_dataloaders * n_batches, "processed": n_val_dataloaders * n_batches, "completed": n_val_dataloaders * n_batches, }, "is_last_batch": True, } model = TestModel(True) trainer = Trainer( default_root_dir=tmpdir, max_epochs=1, val_check_interval=val_check_interval, num_sanity_val_steps=0, enable_progress_bar=False, callbacks=OnExceptionCheckpoint(tmpdir), ) with pytest.raises(CustomException): # will stop during validation trainer.fit(model) assert os.path.exists(ckpt_path) checkpoint = torch.load(ckpt_path)["loops"]["fit_loop"] per_val_train_batches = int(n_batches * val_check_interval) assert checkpoint["epoch_loop.batch_progress"] == { "total": { "ready": per_val_train_batches, "started": per_val_train_batches, "processed": per_val_train_batches, "completed": per_val_train_batches, }, "current": { "ready": per_val_train_batches, "started": per_val_train_batches, "processed": per_val_train_batches, "completed": per_val_train_batches, }, "is_last_batch": val_check_interval == 1, } val_batch_progress = "epoch_loop.val_loop.batch_progress" # "nb_": non-breaking nb_total_val_batch = stop_dataloader * n_batches assert checkpoint[val_batch_progress] == { "total": { "ready": nb_total_val_batch + stop_batch + 1, "started": nb_total_val_batch + stop_batch + 1, "processed": nb_total_val_batch + stop_batch, "completed": nb_total_val_batch + stop_batch, }, "current": { "ready": nb_total_val_batch + stop_batch + 1, "started": nb_total_val_batch + stop_batch + 1, "processed": nb_total_val_batch + stop_batch, "completed": nb_total_val_batch + stop_batch, }, "is_last_batch": False, } model = TestModel(False) trainer = Trainer( default_root_dir=tmpdir, max_epochs=1, val_check_interval=val_check_interval, enable_progress_bar=False, ) trainer.fit(model, ckpt_path=ckpt_path) assert trainer.global_step == expected_global_step state_dict_after_restart = trainer.fit_loop.state_dict() # should get the same values as in the run that did not fail # totals are increased by 1 (the failed batch which never completed) expected = state_dict.copy() assert state_dict_after_restart["epoch_loop.batch_progress"] == expected["epoch_loop.batch_progress"] expected[val_batch_progress]["total"]["ready"] += 1 expected[val_batch_progress]["total"]["started"] += 1 assert state_dict_after_restart[val_batch_progress] == expected[val_batch_progress] @pytest.mark.parametrize("should_fail", [False, True]) @pytest.mark.parametrize("persistent_workers", [False, True]) def test_workers_are_shutdown(tmpdir, should_fail, persistent_workers): # `num_workers == 1` uses `_MultiProcessingDataLoaderIter` # `persistent_workers` makes sure `self._iterator` gets set on the `DataLoader` instance class _TestMultiProcessingDataLoaderIter(_MultiProcessingDataLoaderIter): def __init__(self, *args, dataloader, **kwargs): super().__init__(*args, **kwargs) self.dataloader = dataloader def _shutdown_workers(self): self.dataloader.count_shutdown_workers += 1 super()._shutdown_workers() class TestDataLoader(DataLoader): def __init__(self, *args, **kwargs): super().__init__(*args, **kwargs) self.count_shutdown_workers = 0 def _get_iterator(self): if self.num_workers == 0: return super()._get_iterator() else: self.check_worker_number_rationality() return _TestMultiProcessingDataLoaderIter(self, dataloader=self) train_dataloader = TestDataLoader(RandomDataset(32, 64), num_workers=1, persistent_workers=persistent_workers) val_dataloader = TestDataLoader(RandomDataset(32, 64), num_workers=1, persistent_workers=persistent_workers) class TestCallback(Callback): def on_train_epoch_end(self, trainer, *_): if trainer.current_epoch == 1: raise CustomException max_epochs = 3 model = BoringModel() trainer = Trainer( default_root_dir=tmpdir, limit_train_batches=2, limit_val_batches=2, max_epochs=max_epochs, callbacks=TestCallback() if should_fail else None, ) if should_fail: with pytest.raises(CustomException): trainer.fit(model, train_dataloader, val_dataloader) else: trainer.fit(model, train_dataloader, val_dataloader) assert train_dataloader.count_shutdown_workers == 2 if should_fail else (2 if persistent_workers else max_epochs) # on sanity checking end, the workers are being deleted too. expected = 2 if persistent_workers else (3 if should_fail else max_epochs + 1) assert val_dataloader.count_shutdown_workers == expected