Works as a temporary distributed barrier, currently pytorch
    doesn't implement barrier for NCCL backend.
    Calls all_reduce on dummy tensor and synchronizes with GPU.

def barrier():
    """
    Works as a temporary distributed barrier, currently pytorch
    doesn't implement barrier for NCCL backend.
    Calls all_reduce on dummy tensor and synchronizes with GPU.
    """
    if torch.distributed.is_available() and torch.distributed.is_initialized():
        torch.distributed.all_reduce(torch.cuda.FloatTensor(1))
        torch.cuda.synchronize()