pytorch

5a661e01 - [WIP][Grad Compression] Unittest to verify allreduce_hook parity (#50851)

[WIP][Grad Compression] Unittest to verify allreduce_hook parity (#50851) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/50851 Improves upon the previous unittest to ensure allreduce_hook results in the same gradients as vanilla allreduce in DDP. ghstack-source-id: 120229103 Test Plan: buck build mode/dev-nosan //caffe2/test/distributed:distributed_nccl_fork --keep-going BACKEND=nccl WORLD_SIZE=2 ~/fbcode/buck-out/dev/gen/caffe2/test/distributed/distributed_nccl_fork#binary.par -r test_ddp_hook_parity Reviewed By: SciPioneer Differential Revision: D25963654 fbshipit-source-id: d55eee0aee9cf1da52aa0c4ba1066718aa8fd9a4