pytorch

60241e94 - optimize group_norm (#16216)

optimize group_norm (#16216) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/16216 Optimize GroupNormOp Reviewed By: houseroad Differential Revision: D13754145 fbshipit-source-id: 650f64c81486c6c9d276f2e3325392d5838751ba