Source code for pytorch_lightning.callbacks.gradient_accumulation_scheduler

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Gradient Accumulator

Change gradient accumulation factor according to scheduling.
Trainer also calls ``optimizer.step()`` for the last indivisible step number.


from typing import Any, Dict

import pytorch_lightning as pl
from pytorch_lightning.callbacks.callback import Callback
from pytorch_lightning.utilities.exceptions import MisconfigurationException

[docs]class GradientAccumulationScheduler(Callback): r""" Change gradient accumulation factor according to scheduling. Args: scheduling: scheduling in format {epoch: accumulation_factor} Note: The argument scheduling is a dictionary. Each key represent an epoch and its associated accumulation factor value. Warning: Epoch are zero-indexed c.f it means if you want to change the accumulation factor after 4 epochs, set ``Trainer(accumulate_grad_batches={4: factor})`` or ``GradientAccumulationScheduler(scheduling={4: factor})``. For more info check the example below. Raises: TypeError: If ``scheduling`` is an empty ``dict``, or not all keys and values of ``scheduling`` are integers. IndexError: If ``minimal_epoch`` is less than 0. Example:: >>> from pytorch_lightning import Trainer >>> from pytorch_lightning.callbacks import GradientAccumulationScheduler # from epoch 5, it starts accumulating every 2 batches. Here we have 4 instead of 5 # because epoch (key) should be zero-indexed. >>> accumulator = GradientAccumulationScheduler(scheduling={4: 2}) >>> trainer = Trainer(callbacks=[accumulator]) # alternatively, pass the scheduling dict directly to the Trainer >>> trainer = Trainer(accumulate_grad_batches={4: 2}) """ def __init__(self, scheduling: Dict[int, int]): super().__init__() if not scheduling: # empty dict error raise TypeError("Empty dict cannot be interpreted correct") if any(not isinstance(key, int) or key < 0 for key in scheduling): raise MisconfigurationException( f"Epoch should be an int greater than or equal to 0. Got {list(scheduling.keys())}." ) if any(not isinstance(value, int) or value < 1 for value in scheduling.values()): raise MisconfigurationException( f"Accumulation factor should be an int greater than 0. Got {list(scheduling.values())}." ) minimal_epoch = min(scheduling.keys()) if minimal_epoch < 0: raise IndexError(f"Epochs indexing from 1, epoch {minimal_epoch} cannot be interpreted correct") if minimal_epoch != 0: # if user didnt define first epoch accumulation factor scheduling.update({0: 1}) self.scheduling = scheduling self.epochs = sorted(scheduling.keys()) def going_to_accumulate_grad_batches(self) -> bool: return any(v > 1 for v in self.scheduling.values()) def get_accumulate_grad_batches(self, epoch: int) -> int: accumulate_grad_batches = 1 for iter_epoch in reversed(self.epochs): if epoch >= iter_epoch: accumulate_grad_batches = self.scheduling[iter_epoch] break return accumulate_grad_batches
[docs] def on_train_epoch_start(self, trainer: "pl.Trainer", *_: Any) -> None: trainer.accumulate_grad_batches = self.get_accumulate_grad_batches(trainer.current_epoch)

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