Replace the use of the deprecated torch.distributed.reduce_op with to… (#804)
Replace the use of the deprecated torch.distributed.reduce_op with to… (#804)

Summary:
…rch.distributed.ReduceOp
Pull Request resolved: https://github.com/pytorch/fairseq/pull/804

Differential Revision: D15877033

Pulled By: myleott

fbshipit-source-id: 58e7c39a88b67345a55b761fee4d9f211a5ee82c

pytorch/fairseq,pytorch/fairseq,pytorch/fairseq