pytorch

c29e279f - [DDP] unittest for when params arent used in backward pass (#52384)

[DDP] unittest for when params arent used in backward pass (#52384) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/52384 Adds a simple UT with unittest that we can modify when we enable DDP backward without needing all parameters to get gradient. ghstack-source-id: 122001930 Test Plan: CI Reviewed By: zhaojuanmao Differential Revision: D26482479 fbshipit-source-id: c80bdeea7cf9db35390e385084ef28d64ed239eb