pytorch

4638bd0f - Fix ProcessGroupMPITest.cpp Gather, Scatter and SendRecv. Enable ProcessGroupMPITest (#56709)

Fix ProcessGroupMPITest.cpp Gather, Scatter and SendRecv. Enable ProcessGroupMPITest (#56709) Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/56709 Right now, ProcessGroupMPITest testGather() fails with ``` what(): Gather: number of output tensors should be 0 for non-root [devgpu025:429730] *** Process received signal *** ``` there is a similar issue with testScatter() where number of input/output tensors on source/destination respectively should be 0. In addition testSendRecv(true); fails with ``` terminate called after throwing an instance of 'std::runtime_error' what(): src rank is wrong for recvAnysource ``` since we never populate `srcRanks` Test Plan: Imported from OSS Reviewed By: pbelevich Differential Revision: D28001963 Pulled By: agolynski fbshipit-source-id: c381dfc6f417ee78fbbaf884e567b0485076dfc8