FWIW, the function in ddp.cpp should be considered a private API, only to be used by DistributedDataParallel. For the upcoming release, it was removed and replaced with a function also called broadcast_coalesced in the c10d namespace. See https://github.com/pytorch/pytorch/blob/caa0d0c/torch/csrc/distributed/c10d/comm.h 33. See https://github.com/pytorch/pytorch/pull/20234 20 for the PR that added it.