GitLab

* [fix] FSDP forward pass overlap between compute and all-gather

- much thanks for @cyanguwa for report and @QuentinDuval for debugging it
- a new unit test is added to check for this and ensure we detect
  issue with overlapping and cpu/gpu blocking wait calls

* fix

* fix

* fix

* better assertion outputs

* fix format and tune all_gather mb for CI

* more tuning with non_flatten

* undo an accidental change

* tuning all gather mb and del model

* Update + fix overlapping test to use patched all_gather w/ delay (#672)

* fixing get_cycles_per_ms

* add get_smi_memory

* update the docstring
Co-authored-by: Min Xu <min.xu@acm.org>
Co-authored-by: Myle Ott <myleott@fb.com>

* [fix] add clear_autocast_cache flag

- when training in AMP model with weight dtype32, FSDP may need to
  optionally clear the autocast cache to avoid GPU OOM
- this flag is default false, automatically doing it is a future TODO
- also added a verbose flag to make print(fsdp_model) a bit shorter
- updated the memory test to cover those new code
- added a couple of useful functions in parallel.py and testing.py

* minor

* address comments

* format

* improve the test
Co-authored-by: Min Xu <min.xu@acm.org>

Adds support for:
* Reused layers (e.g. for weight sharing)
* Lazily-constructed layers
* Single-process control via PipeRPCWrapper
* PipelineStyle.AsyncScheudle, which lays the foundation for asynchronous pipeline work by introducing an event loop for each rank/worker to process either activations or gradients as they arrive

Also added examples for multi-process and PipeRPCWrapper

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