pytorch

ce5981e4 - [DDP] Custom buffer reduction (#64513)

[DDP] Custom buffer reduction (#64513) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/64513 Proposal: https://github.com/pytorch/pytorch/issues/63041 Support custom buffer reduction in DDP via hook ghstack-source-id: 138655663 Test Plan: CI Reviewed By: SciPioneer Differential Revision: D30751152 fbshipit-source-id: 257a9d46bb178d8812d4ea5a4d9c6140b8a1791f