[Bugfix] fix xpu communicator (#13368)

Signed-off-by: yan ma <yan.ma@intel.com>

vllm/distributed/device_communicators/xpu_communicator.py

+# SPDX-License-Identifier: Apache-2.0
+
+from typing import Optional
+
+import torch
+import torch.distributed as dist
+from torch.distributed import ProcessGroup
+
+from .base_device_communicator import DeviceCommunicatorBase
+
+
+class XpuCommunicator(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)
+
+    def all_reduce(self, input_) -> torch.Tensor:
+        dist.all_reduce(input_, group=self.device_group)
+        return input_
+
+    def gather(self,
+               input_: torch.Tensor,
+               dst: int = 0,
+               dim: int = -1) -> Optional[torch.Tensor]:
+        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()
+        # For xpu path, gather doesn't work properly together with ray
+        # cluster so we use all_gather instead for now.
+        input_size = input_.size()
+        # Allocate output tensor.
+        output_tensor = torch.empty((self.world_size, ) + input_size,
+                                    dtype=input_.dtype,
+                                    device=input_.device)
+        # All-gather.
+        dist.all_gather_into_tensor(output_tensor,
+                                    input_,
+                                    group=self.device_group)
+        if self.rank_in_group == dst:
+            # Reshape
+            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:])
+        else:
+            output_tensor = None
+        return output_tensor

vllm/platforms/xpu.py

@@ -135,3 +135,7 @@ class XPUPlatform(Platform):
             logger.warning("Unknown device name %s, always use float16",
                            device_name)
             return False
+
+    @classmethod
+    def get_device_communicator_cls(cls) -> str:
+        return "vllm.distributed.device_communicators.xpu_communicator.XpuCommunicator"  # noqa