pytorch

e077a2a2 - [Gradient Compression] Add CppCommHook subclass for supporting the C++ API of communication hook. (#46566)

[Gradient Compression] Add CppCommHook subclass for supporting the C++ API of communication hook. (#46566) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/46566 Only provides an interface. Some built-in implementations will be provided in a follow-up commit. Original PR issue: C++ DDP Communication Hook https://github.com/pytorch/pytorch/issues/46348 ghstack-source-id: 115319038 Test Plan: waitforbuildbot Reviewed By: pritamdamania87 Differential Revision: D24379460 fbshipit-source-id: 8382dc4185c7c01d0ac5b3498e1bead785bccec5