[Misc][Platform] Move use allgather to platform (#14010)

Signed-off-by: Mengqing Cao <cmq0113@163.com>

vllm/model_executor/layers/logits_processor.py

@@ -8,7 +8,6 @@ import torch
 import torch.nn as nn
 
 import vllm.envs as envs
-from vllm.config import get_current_vllm_config
 from vllm.distributed import (tensor_model_parallel_all_gather,
                               tensor_model_parallel_gather)
 from vllm.model_executor.layers.vocab_parallel_embedding import (
@@ -51,11 +50,7 @@ class LogitsProcessor(nn.Module):
         # Soft cap the logits. Used in Gemma 2.
         self.soft_cap = soft_cap
         # Whether to use gather or all-gather to gather the logits.
-        parallel_config = get_current_vllm_config().parallel_config
-        self.use_all_gather = current_platform.is_tpu() \
-            or current_platform.is_neuron() \
-            or envs.VLLM_USE_V1 \
-            or parallel_config.distributed_executor_backend == "external_launcher" # noqa
+        self.use_all_gather = current_platform.use_all_gather()
 
     def forward(
         self,
@@ -83,7 +78,8 @@ class LogitsProcessor(nn.Module):
                 logits *= self.scale
 
             # Apply logits processors (if any).
-            if sampling_metadata is not None:
+            if sampling_metadata is not None and \
+                sampling_metadata.seq_groups is not None:
                 logits = _apply_logits_processors(logits, sampling_metadata)
 
         return logits

vllm/platforms/interface.py

@@ -330,6 +330,19 @@ class Platform:
         """
         return "vllm.distributed.device_communicators.base_device_communicator.DeviceCommunicatorBase"  # noqa
 
+    @classmethod
+    def use_all_gather(cls) -> bool:
+        """
+        Whether to use allgather in LogitsProcessor to gather the logits.
+        """
+        import vllm.envs as envs
+        from vllm.config import get_current_vllm_config
+
+        parallel_config = get_current_vllm_config().parallel_config
+        return (envs.VLLM_USE_V1
+                or parallel_config.distributed_executor_backend
+                == "external_launcher")
+
 
 class UnspecifiedPlatform(Platform):
     _enum = PlatformEnum.UNSPECIFIED

vllm/platforms/neuron.py

@@ -55,3 +55,7 @@ class NeuronPlatform(Platform):
     def is_pin_memory_available(cls) -> bool:
         logger.warning("Pin memory is not supported on Neuron.")
         return False
+
+    @classmethod
+    def use_all_gather(cls) -> bool:
+        return True

vllm/platforms/tpu.py

@@ -119,3 +119,7 @@ class TpuPlatform(Platform):
     @classmethod
     def get_device_communicator_cls(cls) -> str:
         return "vllm.distributed.device_communicators.tpu_communicator.TpuCommunicator"  # noqa
+
+    @classmethod
+    def use_all_gather(cls) -> bool:
+        return True