Revert "Revert "checkpoint consolidation""

This reverts commit 3a9fde915a.

pytorch_lightning/callbacks/base.py

@@ -109,6 +109,10 @@ class Callback(abc.ABC):
         """Called when the epoch ends."""
         pass
 
+    def on_train_epoch_final_end(self, trainer, pl_module: LightningModule) -> None:
+        """Called when at the very end of train epoch."""
+        pass
+
     def on_batch_start(self, trainer, pl_module: LightningModule) -> None:
         """Called when the training batch begins."""
         pass

pytorch_lightning/callbacks/early_stopping.py

@@ -143,6 +143,21 @@ class EarlyStopping(Callback):
 
         self._run_early_stopping_check(trainer)
 
+    def on_train_epoch_final_end(self, trainer, pl_module):
+        from pytorch_lightning.trainer.states import TrainerState
+        if (
+            trainer.state != TrainerState.FITTING or trainer.sanity_checking
+            or not trainer.checkpoint_connector.has_trained
+        ):
+            return
+        # if validation is disabled or should skip, we run early stopping
+        # at end of the training epoch
+        if (
+            trainer.disable_validation
+            or trainer.evaluation_loop.should_skip_evaluation(trainer.num_val_batches)
+        ):
+            self._run_early_stopping_check(trainer)
+
     def _run_early_stopping_check(self, trainer):
         """
         Checks whether the early stopping condition is met

pytorch_lightning/callbacks/lambda_function.py

@@ -53,6 +53,7 @@ class LambdaCallback(Callback):
         on_train_batch_end: Optional[Callable] = None,
         on_train_epoch_start: Optional[Callable] = None,
         on_train_epoch_end: Optional[Callable] = None,
+        on_train_epoch_final_end: Optional[Callable] = None,
         on_validation_epoch_start: Optional[Callable] = None,
         on_validation_epoch_end: Optional[Callable] = None,
         on_test_epoch_start: Optional[Callable] = None,
@@ -155,3 +156,5 @@ class LambdaCallback(Callback):
             self.on_after_backward = on_after_backward
         if on_before_zero_grad is not None:
             self.on_before_zero_grad = on_before_zero_grad
+        if on_train_epoch_final_end is not None:
+            self.on_train_epoch_final_end = on_train_epoch_final_end

pytorch_lightning/callbacks/model_checkpoint.py

@@ -238,6 +238,37 @@ class ModelCheckpoint(Callback):
             return
         self.save_checkpoint(trainer)
 
+    def on_train_epoch_final_end(self, trainer, pl_module):
+        """
+        at the end of each training epoch, checkpoint only when validation is skipped or disabled
+        """
+        print("aaa: epoch {}, step: {}".format(trainer.current_epoch, trainer.global_step))
+        if (
+            self._should_skip_saving_checkpoint(trainer)
+            or not trainer.checkpoint_connector.has_trained
+        ):
+            return
+        # if validation is disabled or should skip, we checkpoint at end of the training epoch
+        if (
+            trainer.disable_validation
+            or trainer.evaluation_loop.should_skip_evaluation(trainer.num_val_batches)
+        ):
+            self.save_checkpoint(trainer)
+
+    def on_train_end(self, trainer, *args, **kwargs) -> None:
+        """
+        checkpoints can be saved at the end of the trianing
+        """
+        trainer.global_step -= 1
+        if (
+            not self._should_skip_saving_checkpoint(trainer)
+            and trainer.checkpoint_connector.has_trained
+        ):
+            if self.save_last and self.verbose:
+                rank_zero_info("Saving latest checkpoint...")
+            self.save_checkpoint(trainer)
+        trainer.global_step += 1
+
     def on_save_checkpoint(self, trainer, pl_module, checkpoint: Dict[str, Any]) -> Dict[str, Any]:
         return {
             "monitor": self.monitor,

pytorch_lightning/trainer/callback_hook.py

@@ -92,6 +92,13 @@ class TrainerCallbackHookMixin(ABC):
         for callback in self.callbacks:
             callback.on_train_epoch_end(self, self.lightning_module, outputs)
 
+    def on_train_epoch_final_end(self) -> None:
+        """
+        Called when at the very end of train epoch.
+        """
+        for callback in self.callbacks:
+            callback.on_train_epoch_final_end(self, self.lightning_module)
+
     def on_validation_epoch_start(self):
         """Called when the epoch begins."""
         for callback in self.callbacks:

pytorch_lightning/trainer/connectors/logger_connector/callback_hook_validator.py

@@ -100,6 +100,11 @@ class CallbackHookNameValidator:
         """Called when the epoch ends."""
         return {"on_step": [False], "on_epoch": [False, True]}
 
+    @staticmethod
+    def _on_train_epoch_final_end_log():
+        """Called when at the very end of train epoch."""
+        return {"on_step": [False], "on_epoch": [False, True]}
+
     @staticmethod
     def _on_validation_epoch_start_log():
         """Called when the epoch begins."""

pytorch_lightning/trainer/training_loop.py

@@ -121,12 +121,6 @@ class TrainLoop:
             return
         self._teardown_already_run = True
 
-        # trigger checkpoint check. need to temporarily decrease the global step to avoid saving duplicates
-        # when a checkpoint was saved at the last step
-        self.trainer.global_step -= 1
-        self.check_checkpoint_callback(should_update=True, is_last=True)
-        self.trainer.global_step += 1
-
         # hook
         self.trainer.call_hook("on_train_end")
 
@@ -145,28 +139,6 @@ class TrainLoop:
         # reset bookkeeping
         self.trainer._running_stage = None
 
-    def check_checkpoint_callback(self, should_update, is_last=False):
-        # TODO bake this logic into the ModelCheckpoint callback
-        if should_update and self.trainer.checkpoint_connector.has_trained:
-            callbacks = self.trainer.checkpoint_callbacks
-
-            if is_last and any(cb.save_last and cb.verbose for cb in callbacks):
-                rank_zero_info("Saving latest checkpoint...")
-
-            model = self.trainer.lightning_module
-
-            for cb in callbacks:
-                cb.on_validation_end(self.trainer, model)
-
-    def check_early_stopping_callback(self, should_update):
-        # TODO bake this logic into the EarlyStopping callback
-        if should_update and self.trainer.checkpoint_connector.has_trained:
-            callbacks = [c for c in self.trainer.callbacks if isinstance(c, EarlyStopping)]
-            model = self.trainer.lightning_module
-
-            for cb in callbacks:
-                cb.on_validation_end(self.trainer, model)
-
     def on_train_epoch_start(self, epoch):
 
         # update training progress in trainer
@@ -562,15 +534,14 @@ class TrainLoop:
         if (val_loop_called and not should_check_val) or should_train_only:
             self.trainer.optimizer_connector.update_learning_rates(interval='epoch')
 
-        if should_train_only:
-            self.check_checkpoint_callback(True)
-            self.check_early_stopping_callback(True)
-
         if should_check_val:
             self.trainer.validating = True
             self.trainer.run_evaluation(on_epoch=True)
             self.trainer.training = True
 
+        if should_train_only:
+            self.trainer.call_hook('on_train_epoch_final_end')
+
         # increment the global step once
         # progress global step according to grads progress
         self.increment_accumulated_grad_global_step()

tests/checkpointing/test_model_checkpoint.py

@@ -609,7 +609,13 @@ def test_model_checkpoint_period(tmpdir, period: int):
     trainer.fit(model)
 
     # check that the correct ckpts were created
-    expected = [f'epoch={e}.ckpt' for e in range(epochs) if not (e + 1) % period] if period > 0 else []
+    final_epoch_ckpt = "epoch={e}.ckpt".format(e=epochs-1)
+    expected = (
+        [f"epoch={e}.ckpt" for e in range(epochs) if not (e + 1) % period and e + 1 != epochs]
+        if period > 0
+        else []
+    )
+    expected.append(final_epoch_ckpt)
     assert set(os.listdir(tmpdir)) == set(expected)
 
 
@@ -631,8 +637,14 @@ def test_model_checkpoint_every_n_val_epochs(tmpdir, every_n_val_epochs):
     trainer.fit(model)
 
     # check that the correct ckpts were created
-    expected = [f'epoch={e}.ckpt' for e in range(epochs)
-                if not (e + 1) % every_n_val_epochs] if every_n_val_epochs > 0 else []
+    # check that the correct ckpts were created
+    final_epoch_ckpt = "epoch={e}.ckpt".format(e=epochs-1)
+    expected = (
+        [f"epoch={e}.ckpt" for e in range(epochs) if not (e + 1) % every_n_val_epochs and e + 1 != epochs]
+        if every_n_val_epochs > 0
+        else []
+    )
+    expected.append(final_epoch_ckpt)
     assert set(os.listdir(tmpdir)) == set(expected)
 
 
@@ -659,8 +671,14 @@ def test_model_checkpoint_every_n_val_epochs_and_period(tmpdir, every_n_val_epoc
     trainer.fit(model)
 
     # check that the correct ckpts were created
-    expected = [f'epoch={e}.ckpt' for e in range(epochs)
-                if not (e + 1) % every_n_val_epochs] if every_n_val_epochs > 0 else []
+    # check that the correct ckpts were created
+    final_epoch_ckpt = "epoch={e}.ckpt".format(e=epochs-1)
+    expected = (
+        [f"epoch={e}.ckpt" for e in range(epochs) if not (e + 1) % every_n_val_epochs and e + 1 != epochs]
+        if every_n_val_epochs > 0
+        else []
+    )
+    expected.append(final_epoch_ckpt)
     assert set(os.listdir(tmpdir)) == set(expected)
 
 
@@ -816,10 +834,15 @@ def test_model_checkpoint_save_last_warning(
         default_root_dir=tmpdir,
         callbacks=[ckpt],
         max_epochs=max_epochs,
+        val_check_interval=0.1,
     )
     with caplog.at_level(logging.INFO):
         trainer.fit(model)
-    assert caplog.messages.count('Saving latest checkpoint...') == (verbose and save_last)
+    if verbose and save_last and not should_validate:
+        # no validation, hence checkpoint triggered at the end of each training epoch
+        assert caplog.messages.count('Saving latest checkpoint...') == False
+    else:
+        assert caplog.messages.count('Saving latest checkpoint...') == (verbose and save_last)
 
 
 def test_model_checkpoint_save_last_checkpoint_contents(tmpdir):

tests/helpers/utils.py

@@ -76,7 +76,7 @@ def reset_seed(seed=0):
 def set_random_master_port():
     reset_seed()
     port = RANDOM_PORTS.pop()
-    os.environ['MASTER_PORT'] = str(port)
+    os.environ['MASTER_PORT'] = "29501"
 
 
 def init_checkpoint_callback(logger):

tests/trainer/logging_/test_logger_connector.py

@@ -300,6 +300,7 @@ def test_call_back_validator(tmpdir):
         'on_train_batch_start',
         'on_train_end',
         'on_train_epoch_end',
+        'on_train_epoch_final_end',
         'on_train_epoch_start',
         'on_train_start',
         'on_validation_batch_end',