GitLab

* minor: changelog and pre-commit

* addressed comment

* update the release doc
Co-authored-by: Min Xu <min.xu.public@gmail.com>

Pre-commit hook fails when run on all files for three reasons:
(see trace below)

1. Trailing whitespace on multiple files
2. mypy fails to load numpy and then subsequently fails to load
LazyModule from pipe.py
3. isort sees issues with known_third_party packages

```
> pre-commit run --all-files

Trim Trailing Whitespace.................................................Failed
- hook id: trailing-whitespace
- exit code: 1
- files were modified by this hook

Fixing docs/source/conf.py
Fixing fairscale/experimental/nn/auto_shard.py
Fixing docs/source/deep_dive/activation_checkpointing.rst
Fixing docs/source/tutorials/pipe.rst
Fixing docs/source/installation_instructions.rst
Fixing docs/source/deep_dive/pipeline_parallelism.rst
Fixing docs/source/tutorials/activation_checkpointing.rst
Fixing docs/source/tutorials/offload_model.rst
Fixing docs/source/deep_dive/oss_sdp_fsdp.rst
Fixing docs/source/what_is_fairscale.rst
Fixing CHANGELOG.md
Fixing fairscale/experimental/nn/offload.py
Fixing docs/source/index.rst
Fixing docs/source/deep_dive/adascale.rst
Fixing README.md
Fixing docs/source/tutorials/oss.rst
Fixing docs/source/deep_dive/offload.rst

Check python ast.........................................................Passed
Check for merge conflicts................................................Passed
Don't commit to branch...................................................Passed
Check for added large files..............................................Passed
Fix End of Files.........................................................Failed
- hook id: end-of-file-fixer
- exit code: 1
- files were modified by this hook

Fixing requirements.txt
Fixing docs/source/getting_started.rst
Fixing docs/source/installation_instructions.rst
Fixing codecov.yml
Fixing docs/source/deep_dive/adascale.rst
Fixing docs/source/tutorials/oss.rst
Fixing docs/source/deep_dive/offload.rst

black....................................................................Passed
flake8...................................................................Passed
seed isort known_third_party.............................................Failed
- hook id: seed-isort-config
- exit code: 1
- files were modified by this hook
isort....................................................................Passed
mypy.....................................................................Failed
- hook id: mypy
- exit code: 2

setup.cfg:45: error: Error importing plugin 'numpy.typing.mypy_plugin': No module named 'numpy'
Found 1 error in 1 file (checked 197 source files)
```

* Improving test coverage on SDP
* using pytest exception catcher

authored-by: Anjali Sridhar <anj@devfair0443.h2.fair>

* tentatively fixing the cpu version of circleci jobs, now pipe tests are the last ones standing
* fixing oss backcompat, trying to fix rpc in old pytorch also
* fixing the file based init in torch 1.5

Adds support for distributing pipeline stages across multiple processes (and therefore multiple machines)
* Adds a style argument to the Pipe constructor, defaulting to PipelineStyle.SingleProcess, but also supporting PipelineStyle.MultiProcess
* Added support for lazy construction of modules (see lazy_construction for an example)
* Added two implementations of inter-process communication: one based on rpc with globally visible queues, one based on send/recv
* Copied all the relevant tests from tests/pipe to tests/pipe_process and modified them to exercise PipelineStyle.MultiProcess

- rename oss_ddp to ShardedDataParallel
- some refactoring
- ShardedDataParallel owns the sharded optimizer, exposed if need be
- some small perf bumps