hao-ai-lab-FastVideo/v2/distributed/device_communicators/cpu_communicator.py

# SPDX-License-Identifier: Apache-2.0
# Adapted from: https://github.com/vllm-project/vllm/blob/main/vllm/distributed/device_communicators/cpu_communicator.py

import os

import torch
from torch.distributed import ProcessGroup

from v2.platforms.interface import CpuArchEnum

from .base_device_communicator import DeviceCommunicatorBase


class CpuCommunicator(DeviceCommunicatorBase):

    def __init__(self,
                 cpu_group: ProcessGroup,
                 device: torch.device | None = None,
                 device_group: ProcessGroup | None = None,
                 unique_name: str = ""):
        super().__init__(cpu_group, device, device_group, unique_name)
        self.dist_module = torch.distributed

        from v2.platforms import current_platform

        if (current_platform.get_cpu_architecture() == CpuArchEnum.X86) and hasattr(
                torch.ops._C, "init_shm_manager") and unique_name.startswith("tp"):
            self.dist_module = _CPUSHMDistributed(self)

    def all_reduce(self,
                   input_: torch.Tensor,
                   op: torch.distributed.ReduceOp | None = torch.distributed.ReduceOp.SUM) -> torch.Tensor:
        self.dist_module.all_reduce(input_, group=self.device_group, op=op)
        return input_

    def gather(self, input_: torch.Tensor, dst: int = 0, dim: int = -1) -> torch.Tensor | None:
        """
        NOTE: We assume that the input tensor is on the same device across
        all the ranks.
        NOTE: `dst` is the local rank of the destination rank.
        """
        world_size = self.world_size
        assert -input_.dim() <= dim < input_.dim(), (f"Invalid dim ({dim}) for input tensor with shape {input_.size()}")
        if dim < 0:
            # Convert negative dim to positive.
            dim += input_.dim()

        # Allocate output tensor.
        gather_list = [torch.empty_like(input_) for _ in range(world_size)] if self.rank_in_group == dst else None

        # Gather.
        self.dist_module.gather(input_, gather_list, dst=self.ranks[dst], group=self.device_group)

        output_tensor = torch.cat(gather_list, dim=dim) if self.rank_in_group == dst else None
        return output_tensor

    def all_gather(self, input_: torch.Tensor, dim: int = -1) -> torch.Tensor:
        if dim < 0:
            # Convert negative dim to positive.
            dim += input_.dim()
        input_size = input_.size()
        # NOTE: we have to use concat-style all-gather here,
        # stack-style all-gather has compatibility issues with
        # torch.compile . see https://github.com/pytorch/pytorch/issues/138795
        output_size = (input_size[0] * self.world_size, ) + input_size[1:]
        # Allocate output tensor.
        output_tensor = torch.empty(output_size, dtype=input_.dtype, device=input_.device)
        # All-gather.
        self.dist_module.all_gather_into_tensor(output_tensor, input_, group=self.device_group)

        # Reshape
        output_tensor = output_tensor.reshape((self.world_size, ) + input_size)
        output_tensor = output_tensor.movedim(0, dim)
        output_tensor = output_tensor.reshape(input_size[:dim] + (self.world_size * input_size[dim], ) +
                                              input_size[dim + 1:])
        return output_tensor


class _CPUSHMDistributed:

    def __init__(self, communicator: CpuCommunicator):
        instance_identifier = os.environ["VLLM_DIST_IDENT"]
        unique_name = communicator.unique_name
        instance_identifier = f"{instance_identifier}-{unique_name}"
        self.communicator = communicator

        group_ranks = [str(rank) for rank in self.communicator.ranks]
        shm_group_identifier = f"[{'-'.join(group_ranks)}]"
        self.group_name = f"{instance_identifier}-{shm_group_identifier}-cpushm"

        self.handle = self._init_cpu_shm()

    def _init_cpu_shm(self) -> int:
        handle = torch.ops._C.init_shm_manager(
            self.group_name,
            self.communicator.world_size,
            self.communicator.rank,
        )
        torch.distributed.barrier(self.communicator.device_group)
        torch.ops._C.join_shm_manager(
            handle,
            self.group_name,
        )
        torch.distributed.barrier(self.communicator.device_group)

        return int(handle)

    def all_reduce(self, input: torch.Tensor, group: ProcessGroup | None = None) -> None:
        torch.ops._C.shm_allreduce(self.handle, input)

    def gather(self,
               input: torch.Tensor,
               gather_list: list[torch.Tensor] | None,
               dst: int = -1,
               group: ProcessGroup | None = None) -> None:
        # Note: different from the torch gather, here we use local dst rank.
        torch.ops._C.shm_gather(self.handle, input, gather_list, torch.distributed.get_group_rank(group, dst))

    def all_gather_into_tensor(self,
                               output: torch.Tensor,
                               input: torch.Tensor,
                               group: ProcessGroup | None = None) -> None:
        torch.ops._C.shm_all_gather(self.handle, input, output)