Pull in fairscale.nn.Pipe into PyTorch. (#44090)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44090
This is an initial commit pulling in the torchgpipe fork at
https://github.com/facebookresearch/fairscale.
The purpose of this commit is to just pull in the code and ensure all tests and
builds work fine. We will slowly modify this to match our intended API
mentioned in https://fb.quip.com/txurAV3zIFox#RPZACAfAKMq. Follow up PRs would
address further changes needed on top of the initial commit..
We're pulling the code into the `torch.distributed._pipeline.sync` package. The
package is private on purpose since there is a lot of work (ex: docs, API
changes etc.) that needs to go in before we can actually officially support
this.
ghstack-source-id: 114864254
Test Plan:
1) waitforbuildbot
2) Ran all tests on my devgpu
Reviewed By: mrshenli
Differential Revision: D23493316
fbshipit-source-id: fe3c8b7dadeeb86abdc00e8a8652491b0b16743a
