3/n inter batch parallelism

CHANGELOG.md

@@ -181,6 +181,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Removed `on_train_epoch_end` from `Accelerator` ([#9035](https://github.com/PyTorchLightning/pytorch-lightning/pull/9035))
 
 
+- Removed `InterBatchProcessor` in favor of `DataLoaderIterDataFetcher` ([#9052](https://github.com/PyTorchLightning/pytorch-lightning/pull/9052))
+
+
 ### Fixed
 
 - Fixed save/load/resume from checkpoint for DeepSpeed Plugin (

pytorch_lightning/core/lightning.py

@@ -454,6 +454,11 @@ def log(
                     f" of {list(self._metric_attributes.values())}"
                 )
 
+        if is_param_in_hook_signature(self.training_step, "dataloader_iter", explicit=True) and batch_size is None:
+            raise MisconfigurationException(
+                "When the `dataloader_iter` is requested within the `training_step`, `batch_size` should be provided."
+            )
+
         results.log(
             self._current_fx_name,
             name,

pytorch_lightning/loops/__init__.py

@@ -17,4 +17,3 @@
 from pytorch_lightning.loops.dataloader import DataLoaderLoop, EvaluationLoop, PredictionLoop  # noqa: F401
 from pytorch_lightning.loops.epoch import EvaluationEpochLoop, PredictionEpochLoop, TrainingEpochLoop  # noqa: F401
 from pytorch_lightning.loops.fit_loop import FitLoop  # noqa: F401
-from pytorch_lightning.loops.processors import IteratorBatchProcessor  # noqa: F401

pytorch_lightning/loops/batch/training_batch_loop.py

@@ -550,9 +550,13 @@ def _build_kwargs(self, batch: Any, batch_idx: int, opt_idx: int, hiddens: Optio
         step_kwargs = OrderedDict([("batch", batch), ("batch_idx", batch_idx)])
 
         lightning_module = self.trainer.lightning_module
+        training_step_fx = getattr(self.trainer.lightning_module, "training_step")
+
+        if is_param_in_hook_signature(training_step_fx, "dataloader_iter", explicit=True):
+            if not is_param_in_hook_signature(training_step_fx, "batch_idx"):
+                del step_kwargs["batch_idx"]
 
         if len(self.trainer.optimizers) > 1:
-            training_step_fx = getattr(lightning_module, "training_step")
             has_opt_idx_in_train_step = is_param_in_hook_signature(training_step_fx, "optimizer_idx")
             if has_opt_idx_in_train_step:
                 if not lightning_module.automatic_optimization:

pytorch_lightning/loops/dataloader/evaluation_loop.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Any, Iterator, List, Optional, Sequence, Union
+from typing import Any, List, Optional, Sequence, Union
 
 from deprecate.utils import void
 from torch.utils.data.dataloader import DataLoader
@@ -98,17 +98,14 @@ def advance(self, *args: Any, **kwargs: Any) -> None:
         """Performs evaluation on one single dataloader"""
         void(*args, **kwargs)
 
+        dataloader_idx: int = self.current_dataloader_idx
         dataloader = self.trainer.accelerator.process_dataloader(self.current_dataloader)
-        dataloader = self.trainer.data_connector.get_profiled_dataloader(
-            dataloader, dataloader_idx=self.current_dataloader_idx
-        )
+        dataloader = self.trainer.data_connector.get_profiled_dataloader(dataloader, dataloader_idx=dataloader_idx)
         dataloader_iter = iter(dataloader)
 
-        dl_max_batches = self._max_batches[self.current_dataloader_idx]
+        dl_max_batches = self._max_batches[dataloader_idx]
 
-        dl_outputs = self.epoch_loop.run(
-            dataloader_iter, self.current_dataloader_idx, dl_max_batches, self.num_dataloaders
-        )
+        dl_outputs = self.epoch_loop.run(dataloader_iter, dataloader_idx, dl_max_batches, self.num_dataloaders)
 
         # store batch level output per dataloader
         if self.should_track_batch_outputs_for_epoch_end:

pytorch_lightning/loops/epoch/evaluation_epoch_loop.py

@@ -37,6 +37,7 @@ def __init__(self) -> None:
         self._num_dataloaders: Optional[int] = None
         self.outputs: List[STEP_OUTPUT] = []
         self.batch_progress = Progress()
+        self.dataloader_iter: Optional[Iterator] = None
 
     @property
     def done(self) -> bool:
@@ -70,6 +71,8 @@ def on_run_start(
         self._dl_max_batches = dl_max_batches
         self._num_dataloaders = num_dataloaders
 
+        self.dataloader_iter = enumerate(dataloader_iter, self.batch_progress.current.ready)
+
     def advance(
         self, dataloader_iter: Iterator, dataloader_idx: int, dl_max_batches: int, num_dataloaders: int
     ) -> None:
@@ -86,7 +89,7 @@ def advance(
         """
         void(dl_max_batches, num_dataloaders)
 
-        batch_idx, (batch, _) = next(dataloader_iter)
+        batch_idx, (batch, _) = next(self.dataloader_iter)
 
         if batch is None:
             raise StopIteration

pytorch_lightning/loops/epoch/training_epoch_loop.py

@@ -11,24 +11,19 @@
 # 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 Any, Dict, Iterator, List, Optional, Tuple, Union
+from typing import Any, Dict, Iterator, List, Optional, Union
 
 import torch
 
 from pytorch_lightning import loops  # import as loops to avoid circular imports
 from pytorch_lightning.loops.batch import TrainingBatchLoop
-from pytorch_lightning.loops.processors import IteratorBatchProcessor
 from pytorch_lightning.trainer.connectors.logger_connector.result import ResultCollection
 from pytorch_lightning.trainer.progress import Progress, SchedulerProgress
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
+from pytorch_lightning.utilities.fetching import AbstractDataFetcher, DataLoaderIterDataFetcher
 from pytorch_lightning.utilities.model_helpers import is_overridden
 from pytorch_lightning.utilities.types import STEP_OUTPUT
 
-# TODO: currently, the batch processor is only a loop when tbptt is enabled.
-# As we introduce more specialized batch processors, we may want to choose a
-# more suitable abstraction for them.
-BATCH_LOOP_TYPE = Optional[Tuple[TrainingBatchLoop, IteratorBatchProcessor]]
-
 
 class TrainingEpochLoop(loops.Loop):
     """
@@ -50,7 +45,7 @@ def __init__(self, min_steps: int, max_steps: int):
         self.batch_progress = Progress()
         self.scheduler_progress = SchedulerProgress()
 
-        self.batch_loop: BATCH_LOOP_TYPE = None
+        self.batch_loop: Optional[TrainingBatchLoop] = None
         self.val_loop: Optional["loops.EvaluationLoop"] = None
 
         self._results = ResultCollection(training=True)
@@ -81,7 +76,7 @@ def done(self) -> bool:
 
     def connect(
         self,
-        batch_loop: BATCH_LOOP_TYPE = None,
+        batch_loop: TrainingBatchLoop = None,
         val_loop: Optional["loops.EvaluationLoop"] = None,
     ) -> None:
         """Optionally connect a custom batch or validation loop to this training epoch loop."""
@@ -102,14 +97,16 @@ def reset(self) -> None:
             self.scheduler_progress.current.reset()
             self.batch_loop.optim_progress.reset_on_epoch()
 
-    def on_run_start(self, *args: Any, **kwargs: Any) -> None:
+    def on_run_start(self, dataloader_iter: Iterator, **kwargs: Any) -> None:
         # hook
         self.trainer.logger_connector.on_epoch_start()
         self.trainer.call_hook("on_epoch_start")
         self.trainer.call_hook("on_train_epoch_start")
         self.trainer.fit_loop.epoch_progress.increment_started()
 
-    def advance(self, dataloader_iter: Iterator, **kwargs: Any) -> None:
+        self._prepare_dataloader_iter(dataloader_iter)
+
+    def advance(self, *args: Any, **kwargs: Any) -> None:
         """Runs a single training batch.
 
         Args:
@@ -118,33 +115,18 @@ def advance(self, dataloader_iter: Iterator, **kwargs: Any) -> None:
         Raises:
             StopIteration: When the epoch is canceled by the user returning -1
         """
-        if isinstance(self.batch_loop, IteratorBatchProcessor):
-            # By contract, when taking `dataloader_iter` as an argument,
-            # `training_step` is responsible for reporting `is_last` in the
-            # result dict, which is used to determine the stop condition for
-            # the epoch. So as long as `advance` is invoked, it's correct to
-            # assume that there are more batches to be processed.
-            self.batch_progress.increment_ready()
-            with self.trainer.profiler.profile("run_training_batch"):
-                batch_output = self.batch_loop.run(dataloader_iter)
-            self.batch_progress.increment_processed()
-            is_last = batch_output.is_last
-        else:
-            _, (batch, is_last) = next(dataloader_iter)
-
-            if not self.trainer.data_connector.train_data_fetcher.store_on_device:
-                with self.trainer.profiler.profile("training_batch_to_device"):
-                    batch = self.trainer.accelerator.batch_to_device(batch)
-
-            # ------------------------------------
-            # TRAINING_STEP + TRAINING_STEP_END
-            # ------------------------------------
-            self.batch_progress.increment_ready()
-
-            with self.trainer.profiler.profile("run_training_batch"):
-                batch_output = self.batch_loop.run(batch, self.batch_idx)
-
-            self.batch_progress.increment_processed()
+        batch_idx, (batch, is_last) = next(self.dataloader_iter)
+
+        if not self.trainer.data_connector.train_data_fetcher.store_on_device:
+            with self.trainer.profiler.profile("training_batch_to_device"):
+                batch = self.trainer.accelerator.batch_to_device(batch)
+
+        self.batch_progress.increment_ready()
+
+        with self.trainer.profiler.profile("run_training_batch"):
+            batch_output = self.batch_loop.run(batch, batch_idx)
+
+        self.batch_progress.increment_processed()
 
         self.is_last_batch = is_last
 
@@ -162,8 +144,7 @@ def advance(self, dataloader_iter: Iterator, **kwargs: Any) -> None:
         processed_batch_end_outputs = self._prepare_outputs(batch_end_outputs, batch_mode=True)
 
         # hook
-        if not isinstance(self.batch_loop, IteratorBatchProcessor):
-            self.trainer.call_hook("on_train_batch_end", processed_batch_end_outputs, batch, self.batch_idx, 0)
+        self.trainer.call_hook("on_train_batch_end", processed_batch_end_outputs, batch, self.batch_idx, 0)
         self.trainer.call_hook("on_batch_end")
         self.trainer.logger_connector.on_batch_end()
 
@@ -404,3 +385,9 @@ def _save_loggers_on_train_batch_end(self) -> None:
         should_flush_logs = self.trainer.logger_connector.should_flush_logs
         if should_flush_logs and self.trainer.is_global_zero and self.trainer.logger is not None:
             self.trainer.logger.save()
+
+    def _prepare_dataloader_iter(self, dataloader_iter: AbstractDataFetcher) -> None:
+        if not isinstance(dataloader_iter, DataLoaderIterDataFetcher):
+            dataloader_iter = enumerate(dataloader_iter, self.batch_idx + 1)
+        # restore iteration
+        self.dataloader_iter = dataloader_iter

pytorch_lightning/loops/fit_loop.py

@@ -14,7 +14,7 @@
 
 import logging
 from contextlib import suppress
-from typing import Iterator, Optional
+from typing import Optional
 
 from pytorch_lightning.loops import Loop
 from pytorch_lightning.loops.epoch import TrainingEpochLoop