datapipes

This a proof-of-concept repository on how torch.utils.data.datapipes can be used as basis for torchvision.datasets.

General observations

• pathlib.Path should be a first-class citizen for paths.
• dp.iter.LoadFilesFromDisk should have a mode parameter. Forcing rb makes it cumbersome to read from plain text files. Maybe even an opener parameter would be better that defaults to open and respects mode.
• Files loaded with get_file_binaries_from_pathnames used in dp.iter.LoadFilesFromDisk are never closed.
• dp.Iter.RoutedDecoder only accepts (path, buffer) inputs, which is not usable for us. Our datasets return a buffer as well as some additional information.
• It feels weird to call dp.iter.LoadFilesFromDisk for a single file, which is usually the case for our datasets.
• I'm aware that this is not possible if we are streaming archives, but if that is not the case, we should be able to read specific files from an archive. Some datasets contain metadata in a separate file that should be available as soon as we create the dataset rather than based on luck when it is stream with the other files.
• dp.iter.Map expects an IterDataPipe rather than a more general Iterable as the other datapipes.
• Instead of ReadFilesFrom(Tar|Zip) there should be ReadFilesFromArchive that automatically detect the underlying archive type.
• dp.iter.ReadFilesFrom(Tar|Zip) should be split in ListFilesIn(Tar|Zip) and LoadFilesFrom(Tar|Zip). Most datasets define some splits of the data so that only a part of the data has to be loaded at all. It would be a good idea to drop unused files before we load them.
• For some reason dp.iter.ReadFilesFrom(Tar|Zip) returns the files in reversed alphabetical order. This makes it weird to align this with corresponding text files, which are usually read from top to bottom.

Datasets

Legend:

• ✔️ : Fully working
• ⭕ : Working, but with a significant performance hit
• ❌ Not working.

For ⭕ and ❌, please check out the README.md in the corresponding folder for details.

torchvision.datasets.	Status
Caltech101	✔️
Caltech256	✔️
CelebA	✔️
CIFAR10 / CIFAR100	✔️
CocoDetection / CocoCaptions	✔️
VOCDetection / VOCSegmentation	✔️
LSUN	❌
ImageNet	✔️
HMDB51	✔️

Notes

• So far, I think the best approach for datasets with related files is to have each individual datapipe to yield a key for the datapoint as well as the data.