fixed extra dataloader bug (#1196)

* fixed extra dataloader bug

* Update pytorch_lightning/trainer/training_loop.py

Co-Authored-By: Jirka Borovec <Borda@users.noreply.github.com>

* updated CHANGELOG

* Small non-repetition change

self.get_model() => model as it was already defined

* Update CHANGELOG.md

* changed argument name to reload_train_dataloader_every_epoch

* fixed doc underline too short

* reverted to `reload_dataloaders_every_epoch`

* fixed val and test reloading

* fixed val and test reloading

Co-authored-by: TevenLeScao <teven.lescao@gmail.com>
Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

CHANGELOG.md

@@ -43,6 +43,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - `Trainer.add_argparse_args` classmethod fixed. Now it adds a type for the arguments ([#1147](https://github.com/PyTorchLightning/pytorch-lightning/pull/1147)).
 - Fixed bug related to type cheking of `ReduceLROnPlateau` lr schedulers([#1114](https://github.com/PyTorchLightning/pytorch-lightning/issues/1114))
 - Fixed a bug to ensure lightning checkpoints to be backward compatible ([#1132](https://github.com/PyTorchLightning/pytorch-lightning/pull/1132))
+- Fixed a bug that created an extra dataloader with active `reload_dataloaders_every_epoch` ([#1181](https://github.com/PyTorchLightning/pytorch-lightning/issues/1181)
 - Fixed all warnings and errors in the docs build process ([#1191](https://github.com/PyTorchLightning/pytorch-lightning/pull/1191))
 - Fixed an issue where `val_percent_check=0` would not disable validation ([#1251](https://github.com/PyTorchLightning/pytorch-lightning/pull/1251))
 - Fixed average of incomplete `TensorRunningMean` ([#1309](https://github.com/PyTorchLightning/pytorch-lightning/pull/1309))

pytorch_lightning/trainer/evaluation_loop.py

@@ -338,14 +338,14 @@ class TrainerEvaluationLoopMixin(ABC):
 
         # select dataloaders
         if test_mode:
-            if self.reload_dataloaders_every_epoch or self.test_dataloaders is None:
+            if self.test_dataloaders is None:
                 self.reset_test_dataloader(model)
 
             dataloaders = self.test_dataloaders
             max_batches = self.num_test_batches
         else:
             # val
-            if self.reload_dataloaders_every_epoch or self.val_dataloaders is None:
+            if self.val_dataloaders is None:
                 self.reset_val_dataloader(model)
 
             dataloaders = self.val_dataloaders
@@ -399,6 +399,15 @@ class TrainerEvaluationLoopMixin(ABC):
         else:
             self.val_progress_bar.close()
 
+        # eventual dataset reloading
+        if test_mode:
+            if self.reload_dataloaders_every_epoch:
+                self.reset_test_dataloader(model)
+        else:
+            # val
+            if self.reload_dataloaders_every_epoch:
+                self.reset_val_dataloader(model)
+
         # Validation/Test end callbacks
         if test_mode:
             self.on_test_end()

pytorch_lightning/trainer/trainer.py

@@ -274,7 +274,6 @@ class Trainer(
                           " and this method will be removed in v0.8.0", DeprecationWarning)
             self.gradient_clip = gradient_clip
 
-        self.reload_dataloaders_every_epoch = reload_dataloaders_every_epoch
         self.progress_bar_refresh_rate = progress_bar_refresh_rate
         self.check_val_every_n_epoch = check_val_every_n_epoch
         self.track_grad_norm = track_grad_norm
@@ -319,6 +318,8 @@ class Trainer(
                           " NaN grads will be printed automatically when detected.",
                           DeprecationWarning)
 
+        self.reload_dataloaders_every_epoch = reload_dataloaders_every_epoch
+
         self.truncated_bptt_steps = truncated_bptt_steps
         self.resume_from_checkpoint = resume_from_checkpoint
         self.shown_warnings = set()

pytorch_lightning/trainer/training_loop.py

@@ -290,7 +290,9 @@ class TrainerTrainLoopMixin(ABC):
         model = self.get_model()
 
         # load data
-        self.reset_train_dataloader(model)
+        # if reload_dataloaders_every_epoch, this is moved to the epoch loop
+        if not self.reload_dataloaders_every_epoch:
+            self.reset_train_dataloader(model)
         self.reset_val_dataloader(model)
 
         # Train start events
@@ -306,6 +308,9 @@ class TrainerTrainLoopMixin(ABC):
         try:
             # run all epochs
             for epoch in range(self.current_epoch, self.max_epochs):
+                # reset train dataloader
+                if self.reload_dataloaders_every_epoch:
+                    self.reset_train_dataloader(model)
                 # set seed for distributed sampler (enables shuffling for each epoch)
                 if self.use_ddp \
                         and hasattr(self.train_dataloader.sampler, 'set_epoch'):
@@ -394,10 +399,6 @@ class TrainerTrainLoopMixin(ABC):
             if self.is_function_implemented('on_epoch_start'):
                 self.get_model().on_epoch_start()
 
-        # reset train dataloader
-        if self.reload_dataloaders_every_epoch:
-            self.reset_train_dataloader(self.get_model())
-
         # track local dataloader so TPU can wrap each epoch
         train_dataloader = self.train_dataloader