Strided masked reduction: mean. (#66784)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66784
cc nikitaved pearu cpuhrsch
Test Plan: Imported from OSS
Reviewed By: saketh-are
Differential Revision: D31838513
Pulled By: cpuhrsch
fbshipit-source-id: 54b99ccf9821832c31976406379939b3c95f41de
