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690fe019f0
Signed-off-by: cascade812 <cascade812@outlook.com> Signed-off-by: Tyler Michael Smith <tyler@neuralmagic.com> Co-authored-by: Tyler Michael Smith <tyler@neuralmagic.com>
132 lines
4.9 KiB
Python
132 lines
4.9 KiB
Python
# SPDX-License-Identifier: Apache-2.0
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from typing import Optional
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import torch
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from torch.distributed import ProcessGroup
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from .base_device_communicator import DeviceCommunicatorBase
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class CudaCommunicator(DeviceCommunicatorBase):
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def __init__(self,
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cpu_group: ProcessGroup,
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device: Optional[torch.device] = None,
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device_group: Optional[ProcessGroup] = None,
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unique_name: str = ""):
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super().__init__(cpu_group, device, device_group, unique_name)
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if "tp" not in unique_name:
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# only tp uses custom allreduce
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use_custom_allreduce = False
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else:
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from vllm.distributed.parallel_state import (
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_ENABLE_CUSTOM_ALL_REDUCE)
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use_custom_allreduce = _ENABLE_CUSTOM_ALL_REDUCE
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use_pynccl = True
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self.use_pynccl = use_pynccl
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self.use_custom_allreduce = use_custom_allreduce
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# lazy import to avoid documentation build error
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from vllm.distributed.device_communicators.custom_all_reduce import (
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CustomAllreduce)
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from vllm.distributed.device_communicators.pynccl import (
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PyNcclCommunicator)
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self.pynccl_comm: Optional[PyNcclCommunicator] = None
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if use_pynccl and self.world_size > 1:
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self.pynccl_comm = PyNcclCommunicator(
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group=self.cpu_group,
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device=self.device,
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)
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self.ca_comm: Optional[CustomAllreduce] = None
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if use_custom_allreduce and self.world_size > 1:
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# Initialize a custom fast all-reduce implementation.
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self.ca_comm = CustomAllreduce(
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group=self.cpu_group,
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device=self.device,
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)
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def all_reduce(self, input_):
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# always try custom allreduce first,
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# and then pynccl.
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ca_comm = self.ca_comm
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if ca_comm is not None and not ca_comm.disabled and \
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ca_comm.should_custom_ar(input_):
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out = ca_comm.custom_all_reduce(input_)
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assert out is not None
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return out
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pynccl_comm = self.pynccl_comm
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assert pynccl_comm is not None
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out = pynccl_comm.all_reduce(input_)
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if out is None:
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# fall back to the default all-reduce using PyTorch.
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# this usually happens during testing.
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# when we run the model, allreduce only happens for the TP
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# group, where we always have either custom allreduce or pynccl.
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out = input_.clone()
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torch.distributed.all_reduce(out, group=self.device_group)
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return out
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def reduce_scatter(self, input_: torch.Tensor, dim: int = -1):
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world_size = self.world_size
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pynccl_comm = self.pynccl_comm
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assert pynccl_comm is not None
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if dim < 0:
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# Convert negative dim to positive.
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dim += input_.dim()
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# Note: This will produce an incorrect answer if we don't make
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# the input_tensor contiguous. Possible bug in reduce_scatter_tensor?
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input_tensor = input_.movedim(0, dim).contiguous()
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assert input_tensor.shape[0] % world_size == 0
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chunk_size = input_tensor.shape[0] // world_size
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output_shape = (chunk_size, ) + input_tensor.shape[1:]
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output = torch.empty(output_shape,
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dtype=input_tensor.dtype,
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device=input_tensor.device)
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pynccl_comm.reduce_scatter(output, input_)
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# Reshape before returning
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return output.movedim(0, dim).contiguous()
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def send(self, tensor: torch.Tensor, dst: Optional[int] = None) -> None:
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"""Sends a tensor to the destination rank in a non-blocking way"""
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"""NOTE: `dst` is the local rank of the destination rank."""
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if dst is None:
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dst = (self.rank_in_group + 1) % self.world_size
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pynccl_comm = self.pynccl_comm
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if pynccl_comm is not None and not pynccl_comm.disabled:
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pynccl_comm.send(tensor, dst)
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else:
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torch.distributed.send(tensor, self.ranks[dst], self.device_group)
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def recv(self,
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size: torch.Size,
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dtype: torch.dtype,
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src: Optional[int] = None) -> torch.Tensor:
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"""Receives a tensor from the source rank."""
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"""NOTE: `src` is the local rank of the source rank."""
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if src is None:
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src = (self.rank_in_group - 1) % self.world_size
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tensor = torch.empty(size, dtype=dtype, device=self.device)
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pynccl_comm = self.pynccl_comm
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if pynccl_comm is not None and not pynccl_comm.disabled:
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pynccl_comm.recv(tensor, src)
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else:
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torch.distributed.recv(tensor, self.ranks[src], self.device_group)
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return tensor
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def destroy(self):
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if self.pynccl_comm is not None:
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self.pynccl_comm = None
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if self.ca_comm is not None:
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self.ca_comm = None
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