GitLab

* Fix gradient accumulation

Add ``is_scaled_loss`` flag to support both scaled / unscaled loss
Fix ``test_grad_accum`` and``test_set_num_gradients_to_accumulate``

* Add a method to scale grad for grad_accum using unscaled loss

- Revert the changes in `step` method
- Add a method `scale_grad_by_num_grads_to_accum`to handle gradient accumulation using unscaled loss more explicitly
- Add gradient tests

* Implement _compute_corr_mean_between_grads

* Improve tests and comments

* Use ubuntu-20.04 instead of latest

Use ubuntu-20.04 to fix the `arch x64 not found` issue
[Version 3.10 with arch x64 not found actions/setup-python#401](https://github.com/actions/setup-python/issues/401)

* Switch flake8 from gitlab to github

Flake8 was moved to Github
See discussions https://www.reddit.com/r/Python/comments/yvfww8/flake8_took_down_the_gitlab_repository_in_favor/

* Fix scikit-learn package

* Update PyTorch versions

* Resolve comments from Min

* Minor fix

* Disable broken tests for new versions of PyTorch

This is no longer needed since isort's version is 5.10

Also fix black version to 22.3.0 to fix issue with click
dependency.

Update files that now fail with new version of black {a = 2 ** 4} ->
{a = 2**4}

* copyright headers

* isort and pyproject.toml

* precommit and requirement for isort-seed-config

* mypy

* dummy change

* numpy version for pre-commit

* fix mypy issue caused by numpy
Co-authored-by: Min Xu <min.xu.public@gmail.com>

* update changelog

* [skip ci] removed requirements-test.txt

* [skip ci] updating changelog

* [skip ci] add PR numbers

* replacing requirements-test.txt by requirements-dev.txt

* [skip ci] changing requirements-test to requirements-dev in pre-commit and requirements-benchmarks

* [skip ci] mark manual static analysis checks as deprecated

* empty commit to trigger ci

* [skip ci] updating changelog

* [skip ci] addressing comments

* addressing more comments

* adding pre-commit files

* applying pre-commit to all files

* adding no-strict-optional argument to mypy in circle ci config

* fix typo

* updating python versions

* [skip ci] remove extra args

* adding python 3.9

* [skip ci] set pre-commit version in requirements-dev.txt

* set CACHE_VERSION

* move linters from circleci to github actions

* update python version

* update python version in benchmarks_2

* moving to python 3.9.7

* update master branch to main

* added FAQ about updating the branch from master to main

* fixed some false positive correction

* added what is new section

* fixed the quoted code area

* added release what is new section

* added a step in release.md

* fixed a word

* 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