Refactor tensor_parallel and comm_utils (vllm-project#2814)

### What this PR does / why we need it?
1. Move ops/comm_utils to ops/moe/comm_utils
2. Move distributed/tensor_parallel/gather_from_sequence_parallel_region
to ops/moe/comm_utils
3. Delete distributed/tensor_parallel

### Does this PR introduce _any_ user-facing change?
no

### How was this patch tested?
e2e & ut

- vLLM version: main
- vLLM main:
vllm-project/vllm@a1213fa

---------

Signed-off-by: wuweiqiang24 <1005334931@qq.com>
Signed-off-by: wuweiqiang24 <wuweiqiang11@huawei.com>
Signed-off-by: Yizhou Liu <liu_yizhou@outlook.com>

Author: wuweiqiang24

tests/ut/distributed/test_distributed_tensor_parallel.py

@@ -0,0 +1,98 @@
+#
+# Copyright (c) 2025 Huawei Technologies Co., Ltd. All Rights Reserved.
+# Copyright 2023 The vLLM team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# This file is a part of the vllm-ascend project.
+
+import pytest
+import torch
+from pytest_mock import MockerFixture
+
+from tests.ut.base import PytestBase
+from vllm_ascend.ops.moe.comm_utils import (
+    _gather_along_first_dim, async_all_to_all,
+    gather_from_sequence_parallel_region)
+
+
+class TestDistributedCommunication(PytestBase):
+
+    @pytest.fixture(autouse=True)
+    def context(self, mocker: MockerFixture):
+        mocker.patch("torch.npu.current_device", return_value="cpu")
+        mocker.patch("torch.distributed.get_world_size", return_value=4)
+
+        mocker.patch("torch.distributed.get_rank", return_value=0)
+
+    @pytest.mark.parametrize(
+        "input_tensor, output_split_sizes, input_split_sizes",
+        [(torch.randn(8, 16), [2, 2, 2, 2], [2, 2, 2, 2]),
+         (torch.randn(16, 32), None, None)])
+    def test_async_all_to_all(self, input_tensor, output_split_sizes,
+                              input_split_sizes, mocker: MockerFixture):
+        """Test async_all_to_all"""
+        mock_group = mocker.MagicMock()
+        mocker.patch("torch.distributed.all_to_all_single",
+                     return_value=mocker.MagicMock())
+
+        _, a2a_out, handle = async_all_to_all(input_tensor, output_split_sizes,
+                                              input_split_sizes, mock_group)
+
+        # Check if the output tensor is created properly
+        if output_split_sizes is None:
+            assert a2a_out.shape == input_tensor.shape
+        else:
+            total_output_size = sum(output_split_sizes)
+            expected_shape = [total_output_size] + list(
+                input_tensor.size())[1:]
+            assert a2a_out.shape == torch.Size(expected_shape)
+
+        # Ensure handle is returned from async operation
+        assert handle is not None
+        assert isinstance(handle, mocker.MagicMock)
+
+    @pytest.mark.parametrize("world_size, test_tensor, expected",
+                             [(1, torch.randn(8, 16), (8, 16)),
+                              (4, torch.randn(8, 16), (32, 16))])
+    def test_gather_along_first_dim(self, test_tensor, expected, world_size,
+                                    mocker: MockerFixture):
+        """Test _gather_along_first_dim"""
+        mocker.patch("torch.distributed.get_world_size",
+                     return_value=world_size)
+
+        result = _gather_along_first_dim(test_tensor, mocker.MagicMock())
+
+        assert result.shape == expected
+
+    @pytest.mark.parametrize("input_tensor, output_split_sizes",
+                             [(torch.randn(8, 16), None),
+                              (torch.randn(8, 16), [2, 2, 2, 2])])
+    def test_gather_from_sequence_parallel_region(self, input_tensor,
+                                                  output_split_sizes,
+                                                  mocker: MockerFixture):
+        """Test gather_from_sequence_parallel_region"""
+        mock_group = mocker.MagicMock()
+
+        result = gather_from_sequence_parallel_region(input_tensor, mock_group,
+                                                      output_split_sizes)
+
+        # If output_split_sizes is not provided, result should have expanded first dimension by world size
+        if output_split_sizes is None:
+            expected_shape = [input_tensor.shape[0] * 4] + list(
+                input_tensor.shape[1:])
+            assert result.shape == torch.Size(expected_shape)
+        else:
+            # If output_split_sizes is provided, result shape is dictated by sum of output_split_sizes
+            expected_shape = [sum(output_split_sizes)] + list(
+                input_tensor.shape[1:])
+            assert result.shape == torch.Size(expected_shape)

tests/ut/ops/test_comm_utils.py

@@ -348,7 +348,7 @@ def setUp(self):
         self.mock_npu_moe_token_unpermute.return_value = torch.randn(8, 16)
 
         # Mock async_all_to_all
-        patcher6 = patch('vllm_ascend.ops.comm_utils.async_all_to_all')
+        patcher6 = patch('vllm_ascend.ops.moe.comm_utils.async_all_to_all')
         self.mock_async_all_to_all = patcher6.start()
         self.addCleanup(patcher6.stop)
         self.mock_async_all_to_all.return_value = (None, torch.randn(16, 16),