Unit Test for run_dp_sharded_vision_model (#19103)

Signed-off-by: Siqi Yan <siqi@meta.com>
Co-authored-by: Siqi Yan <siqi@meta.com>

Author: cryptopic

tests/multimodal/test_utils.py

@@ -9,12 +9,21 @@
 
 import numpy as np
 import pytest
+import torch
+import torch.multiprocessing as mp
 from PIL import Image, ImageChops
 
+from tests.utils import multi_gpu_test
+from vllm.distributed import get_tensor_model_parallel_world_size
+from vllm.distributed.parallel_state import (init_distributed_environment,
+                                             initialize_model_parallel)
 from vllm.multimodal.image import convert_image_mode
 from vllm.multimodal.inputs import PlaceholderRange
 from vllm.multimodal.utils import (MediaConnector,
-                                   merge_and_sort_multimodal_metadata)
+                                   merge_and_sort_multimodal_metadata,
+                                   run_dp_sharded_vision_model)
+from vllm.platforms import current_platform
+from vllm.utils import get_open_port, update_environment_variables
 
 if TYPE_CHECKING:
     from vllm.multimodal.hasher import MultiModalHashDict
@@ -413,3 +422,90 @@ def test_merge_and_sort_multimodal_metadata_with_interleaving():
         assert modalities == expected_modalities
         assert ranges == expected_ranges
         assert hashes == expected_hashes
+
+
+class SimpleLinearModel(torch.nn.Module):
+    """A simple linear vision model for testing."""
+
+    def __init__(self, input_dim: int = 3 * 224 * 224, output_dim: int = 32):
+        super().__init__()
+        self.flatten = torch.nn.Flatten()
+        self.linear = torch.nn.Linear(input_dim, output_dim)
+
+    def forward(self, x: torch.Tensor):
+        # Flatten the input and apply linear transformation
+        x = self.flatten(x)
+        return self.linear(x)
+
+
+@multi_gpu_test(num_gpus=2)
+@pytest.mark.parametrize(
+    "batch_size",
+    [
+        1,  # Single image
+        4,  # Small batch
+        5,  # Odd batch size (for testing padding)
+    ],
+)
+def test_run_dp_sharded_vision_model(batch_size: int):
+    world_size = 2
+    # Launch processes
+    mp.spawn(
+        run_dp_sharded_vision_model_vs_direct,
+        args=(
+            world_size,
+            batch_size,
+            get_open_port(),
+        ),
+        nprocs=world_size,
+    )
+
+
+def run_dp_sharded_vision_model_vs_direct(local_rank: int, world_size: int,
+                                          batch_size: int, master_port: int):
+    """
+    Test that run_dp_sharded_vision_model produces the same results as 
+    calling the model directly.
+    """
+
+    # Set random seed for reproducibility
+    current_platform.seed_everything(0)
+
+    device = torch.device(f"cuda:{local_rank}")
+    torch.cuda.set_device(device)
+    torch.set_default_device(device)
+
+    update_environment_variables({
+        'RANK': str(local_rank),
+        'LOCAL_RANK': str(local_rank),
+        'WORLD_SIZE': str(world_size),
+        'MASTER_ADDR': 'localhost',
+        'MASTER_PORT': str(master_port),
+    })
+
+    # initialize distributed
+    init_distributed_environment()
+    initialize_model_parallel(tensor_model_parallel_size=world_size)
+
+    # Create a test input tensor
+    image_input = torch.randn(batch_size, 3, 224, 224)
+
+    # Create a simple linear model
+    vision_model = SimpleLinearModel()
+
+    # Run the model directly on the full input
+    with torch.inference_mode():
+        direct_output = vision_model(image_input)
+
+    # Run the model through the sharded function
+    with torch.inference_mode():
+        sharded_output = run_dp_sharded_vision_model(image_input, vision_model)
+
+    # Check that the world size is setup correctly
+    assert get_tensor_model_parallel_world_size() == world_size
+
+    # Check that the outputs have the same shape
+    assert direct_output.shape == sharded_output.shape
+
+    # Check that the outputs are close (they should be identical)
+    assert torch.allclose(direct_output, sharded_output, rtol=1e-5, atol=1e-5)