vllm.distributed.device_communicators.tpu_communicator

class TpuCommunicator(DeviceCommunicatorBase):

    def __init__(self,
                 cpu_group: ProcessGroup,
                 device: Optional[torch.device] = None,
                 device_group: Optional[ProcessGroup] = None,
                 unique_name: str = ""):
        super().__init__(cpu_group, device, device_group, unique_name)

        # NOTE(woosuk): When using TP > 1 on TPUs, every TPU on the same node
        # must be used together. Therefore, the local rank and world size can
        # be simply calculated as follows.
        global_rank = self.global_rank
        global_world_size = self.global_world_size

        if USE_RAY:
            logger.info("TpuCommunicator initialized with RAY")
            # Calculate how many TPU nodes are in the current deployment. This
            # is the Ray placement group if it is deployed with Ray. Default
            # to the number of TPU nodes in the Ray cluster. The number of TPU
            # nodes is computed by the total number of TPUs divided by the
            # number of TPU accelerators per node, to account for clusters
            # with both CPUs and TPUs.
            num_nodes = ray_utils.get_num_tpu_nodes()
            num_nodes_in_pg = ray_utils.get_num_nodes_in_placement_group()
            if num_nodes_in_pg > 0:
                num_nodes = num_nodes_in_pg

            local_world_size = global_world_size // num_nodes
            local_rank = global_rank % local_world_size
        else:
            logger.info("TpuCommunicator initialized with MP")
            # Sanity: Verify we run on a single host
            num_hosts = torch_xla.tpu.num_tpu_workers()
            assert num_hosts == 1

            # Get the current number of TPUs (we have locally)
            local_world_size = torch_xla.tpu.num_available_chips()

            # Get current rank
            local_rank = global_rank % local_world_size

        # Ensure environment variables are set for multihost deployments.
        # On GKE, this is needed for libtpu and TPU driver to know which TPU
        # chip is actually visible. Otherwise the TPU driver will fail to
        # initialize because the number of devices would be different from
        # the number of visible worker addresses.
        os.environ["CLOUD_TPU_TASK_ID"] = str(global_rank)
        os.environ["TPU_VISIBLE_CHIPS"] = str(local_rank)

        pjrt.initialize_multiprocess(local_rank, local_world_size)
        xr._init_world_size_ordinal()
        self.groups = create_optimized_replica_groups()

    def all_reduce(self, input_: torch.Tensor) -> torch.Tensor:
        # TODO: Remove the groups specification after XLA compiler can support
        # auto-reordering the ring order for all-reduce.
        return xm.all_reduce(xm.REDUCE_SUM, input_, groups=self.groups)

    def all_gather(self, input_: torch.Tensor, dim: int = -1) -> torch.Tensor:
        assert dim == -1, "TPUs only support dim=-1 for all-gather."
        return xm.all_gather(input_, dim=dim)