returnn.torch.data.returnn_dataset_wrapper

Wrapper for RETURNN datasets.

We make use of torch.utils.data.IterDataPipe.

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetResetDefaultEpochCounterCallback(dataset: Dataset, *, epoch0: int = 0)

Default for reset_callback. Has an internal counter for the epoch, starting by default at epoch 1 (RETURNN convention).

Parameters:

• dataset – RETURNN dataset.

• epoch0 – Epoch from which the dataset sequence ordering should start. It will actually be epoch0+1 for the first epoch, since __call__() will increment it. By default 0 since next __call__() will increment, thus we start at epoch 1.

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetResetMpSharedEpochCallback(dataset: Dataset, epoch_mp_shared: Value)

Can be used as reset_callback.

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetResetNoOpCallback

Can be used as reset_callback.

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetIterDataPipe(returnn_dataset: Dataset, *, reset_callback: Callable[[], None] | None = None)

Converts a RETURNN dataset into a PyTorch IterableDataset.

Parameters:

• returnn_dataset – dataset to be wrapped

• reset_callback – callback function to be called when the dataset is reset, e.g. to init the epoch. ReturnnDatasetResetDefaultEpochCounterCallback(returnn_dataset) is the default.

reset()

This is called by PyTorch DataLoader mechanism once we create a new iterator over the DataLoader. This happens at the beginning of each epoch.

(Note: The mechanism where reset() is actually called is very obfuscated in PyTorch. As I understand it, there is a IterDataPipe metaclass (_IterDataPipeMeta) which automatically registers a hook on __iter__ via hook_iterator. Deep inside the complex logic of this hook, it calls _set_datapipe_valid_iterator_id which then calls reset().)

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetPerEpochMapDataPipe

Converts a RETURNN dataset into a PyTorch map-style Dataset.

reset()

Returns:

class returnn.torch.data.returnn_dataset_wrapper.ReturnnDatasetFullMapDataPipe

Converts a RETURNN dataset into a PyTorch map-style Dataset. This is over the full dataset, using the default ordering. RETURNN-dataset-side sorting/shuffling is not supported here. Sorting/shuffling is intended to be done in the further PyTorch data pipeline.