test_weight_transfer.py

# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Tests for weight transfer engine backends.

Unit tests for engine classes (parsing, validation, registry).
Integration test for NCCL weight transfer between processes using Ray.
"""

from unittest.mock import MagicMock

import pytest
import ray
import torch

from vllm.config.parallel import ParallelConfig
from vllm.config.weight_transfer import WeightTransferConfig
from vllm.distributed.weight_transfer import WeightTransferEngineFactory
from vllm.distributed.weight_transfer.nccl_engine import (
    NCCLWeightTransferEngine,
    NCCLWeightTransferInitInfo,
    NCCLWeightTransferUpdateInfo,
)
from vllm.utils.network_utils import get_open_port


def create_mock_parallel_config(
    rank: int = 0,
    world_size: int = 1,
    dp_rank: int = 0,
) -> ParallelConfig:
    """Create a mock ParallelConfig for testing."""
    config = MagicMock(spec=ParallelConfig)
    config.rank = rank
    config.world_size = world_size
    config.data_parallel_rank = dp_rank
    return config


# --- Unit Tests: NCCLWeightTransferUpdateInfo Validation ---


class TestNCCLWeightTransferUpdateInfoValidation:
    """Test NCCLWeightTransferUpdateInfo dataclass validation."""

    def test_valid_update_info(self):
        """Test creating valid NCCLWeightTransferUpdateInfo."""
        info = NCCLWeightTransferUpdateInfo(
            names=["layer.weight", "layer.bias"],
            dtype_names=["float32", "float32"],
            shapes=[[10, 10], [10]],
        )
        assert info.names == ["layer.weight", "layer.bias"]
        assert info.dtype_names == ["float32", "float32"]
        assert info.shapes == [[10, 10], [10]]

    def test_mismatched_dtype_names_raises(self):
        """Test that mismatched dtype_names length raises ValueError."""
        with pytest.raises(ValueError, match="dtype_names"):
            NCCLWeightTransferUpdateInfo(
                names=["layer.weight", "layer.bias"],
                dtype_names=["float32"],  # Only one dtype
                shapes=[[10, 10], [10]],
            )

    def test_mismatched_shapes_raises(self):
        """Test that mismatched shapes length raises ValueError."""
        with pytest.raises(ValueError, match="shapes"):
            NCCLWeightTransferUpdateInfo(
                names=["layer.weight", "layer.bias"],
                dtype_names=["float32", "float32"],
                shapes=[[10, 10]],  # Only one shape
            )

    def test_empty_lists_valid(self):
        """Test that empty lists are valid."""
        info = NCCLWeightTransferUpdateInfo(
            names=[],
            dtype_names=[],
            shapes=[],
        )
        assert len(info.names) == 0


# --- Unit Tests: Engine Parsing ---


class TestNCCLEngineParsing:
    """Test NCCLWeightTransferEngine parsing methods."""

    def test_parse_init_info_valid(self):
        """Test parsing valid init info dict."""
        config = WeightTransferConfig(backend="nccl")
        parallel_config = create_mock_parallel_config()
        engine = NCCLWeightTransferEngine(config, parallel_config)

        init_info = engine.parse_init_info(
            {
                "master_address": "127.0.0.1",
                "master_port": 12345,
                "rank_offset": 1,
                "world_size": 3,
            }
        )

        assert isinstance(init_info, NCCLWeightTransferInitInfo)
        assert init_info.master_address == "127.0.0.1"
        assert init_info.master_port == 12345
        assert init_info.rank_offset == 1
        assert init_info.world_size == 3

    def test_parse_init_info_missing_field_raises(self):
        """Test parsing init info with missing required field."""
        config = WeightTransferConfig(backend="nccl")
        parallel_config = create_mock_parallel_config()
        engine = NCCLWeightTransferEngine(config, parallel_config)

        with pytest.raises(ValueError, match="Invalid init_info"):
            engine.parse_init_info(
                {
                    "master_address": "127.0.0.1",
                    # Missing master_port, rank_offset, world_size
                }
            )

    def test_parse_update_info_valid(self):
        """Test parsing valid update info dict."""
        config = WeightTransferConfig(backend="nccl")
        parallel_config = create_mock_parallel_config()
        engine = NCCLWeightTransferEngine(config, parallel_config)

        update_info = engine.parse_update_info(
            {
                "names": ["w1", "w2"],
                "dtype_names": ["float32", "bfloat16"],
                "shapes": [[100, 100], [50]],
            }
        )

        assert isinstance(update_info, NCCLWeightTransferUpdateInfo)
        assert update_info.names == ["w1", "w2"]
        assert update_info.dtype_names == ["float32", "bfloat16"]
        assert update_info.shapes == [[100, 100], [50]]


# --- Unit Tests: Engine Registry ---


class TestEngineRegistry:
    """Test weight transfer engine registry."""

    def test_create_engine_nccl(self):
        """Test factory creates NCCL engine."""
        config = WeightTransferConfig(backend="nccl")
        parallel_config = create_mock_parallel_config()
        engine = WeightTransferEngineFactory.create_engine(config, parallel_config)
        assert isinstance(engine, NCCLWeightTransferEngine)

    def test_create_engine_invalid_backend(self):
        """Test factory raises for invalid backend."""
        config = WeightTransferConfig(backend="invalid")
        parallel_config = create_mock_parallel_config()
        with pytest.raises(ValueError, match="Invalid weight transfer backend"):
            WeightTransferEngineFactory.create_engine(config, parallel_config)

    def test_register_duplicate_raises(self):
        """Test registering duplicate engine name raises."""
        with pytest.raises(ValueError, match="already registered"):
            WeightTransferEngineFactory.register_engine(
                "nccl", NCCLWeightTransferEngine
            )


# --- Test receive_weights without init raises ---


def test_nccl_receive_weights_without_init_raises():
    """Test that receive_weights raises if init_transfer_engine wasn't called."""
    if torch.cuda.device_count() < 1:
        pytest.skip("Need at least 1 GPU for this test")

    config = WeightTransferConfig(backend="nccl")
    parallel_config = create_mock_parallel_config()
    engine = NCCLWeightTransferEngine(config, parallel_config)

    update_info = NCCLWeightTransferUpdateInfo(
        names=["w"],
        dtype_names=["float32"],
        shapes=[[10]],
    )

    with pytest.raises(RuntimeError, match="not initialized"):
        engine.receive_weights(update_info, lambda x: None)


# --- Integration Test: NCCL Weight Transfer Between Ray Tasks ---


@ray.remote(num_gpus=1)
def trainer_broadcast_tensor(
    master_address: str,
    master_port: int,
    world_size: int,
    tensor_shape: list[int],
    tensor_dtype: str,
) -> bool:
    """Trainer task that broadcasts a tensor via NCCL."""
    import torch

    from vllm.distributed.device_communicators.pynccl import PyNcclCommunicator
    from vllm.distributed.utils import StatelessProcessGroup

    # Create process group as rank 0 (trainer)
    pg = StatelessProcessGroup.create(
        host=master_address,
        port=master_port,
        rank=0,
        world_size=world_size,
    )
    # Ray sets CUDA_VISIBLE_DEVICES, so device 0 is the assigned GPU
    comm = PyNcclCommunicator(pg, device=0)

    # Create and broadcast the tensor
    dtype = getattr(torch, tensor_dtype)
    tensor_to_send = torch.ones(tensor_shape, dtype=dtype, device="cuda:0")
    comm.broadcast(tensor_to_send, src=0, stream=torch.cuda.current_stream())
    torch.cuda.synchronize()

    return True


@ray.remote(num_gpus=1)
def inference_receive_tensor(
    master_address: str,
    master_port: int,
    world_size: int,
    tensor_shape: list[int],
    tensor_dtype: str,
) -> dict:
    """Inference task that receives tensor via NCCLWeightTransferEngine."""
    from unittest.mock import MagicMock

    import torch

    from vllm.config.parallel import ParallelConfig
    from vllm.config.weight_transfer import WeightTransferConfig
    from vllm.distributed.weight_transfer.nccl_engine import (
        NCCLWeightTransferEngine,
        NCCLWeightTransferInitInfo,
        NCCLWeightTransferUpdateInfo,
    )

    # Create engine with mock parallel config
    config = WeightTransferConfig(backend="nccl")
    parallel_config = MagicMock(spec=ParallelConfig)
    parallel_config.rank = 0
    parallel_config.world_size = 1
    parallel_config.data_parallel_rank = 0

    engine = NCCLWeightTransferEngine(config, parallel_config)

    # Initialize the engine (joins as rank 1)
    init_info = NCCLWeightTransferInitInfo(
        master_address=master_address,
        master_port=master_port,
        rank_offset=1,  # Trainer is rank 0, we become rank 1
        world_size=world_size,
    )
    engine.init_transfer_engine(init_info)

    # Receive weights with a no-op load_weights that captures the tensor
    received_tensors = []

    def noop_load_weights(weights: list[tuple[str, torch.Tensor]]):
        for name, tensor in weights:
            # Clone tensor to keep it after engine cleans up
            received_tensors.append((name, tensor.clone()))

    update_info = NCCLWeightTransferUpdateInfo(
        names=["test.weight"],
        dtype_names=[tensor_dtype],
        shapes=[tensor_shape],
    )
    engine.receive_weights(update_info, noop_load_weights)
    torch.cuda.synchronize()

    # Verify we received the tensor
    success = False
    received_shape = None
    received_sum = None

    if len(received_tensors) == 1:
        name, tensor = received_tensors[0]
        received_shape = list(tensor.shape)
        received_sum = tensor.sum().item()
        # Check shape matches and values are all 1s (trainer sends ones)
        if received_shape == tensor_shape:
            expected_sum = 1.0 * torch.tensor(tensor_shape).prod().item()
            if abs(received_sum - expected_sum) < 0.01:
                success = True

    engine.shutdown()

    return {
        "success": success,
        "received_shape": received_shape,
        "received_sum": received_sum,
    }


@pytest.mark.skipif(
    torch.cuda.device_count() < 2,
    reason="Need at least 2 GPUs to run NCCL weight transfer test.",
)
def test_nccl_weight_transfer_between_processes():
    """Test NCCL weight transfer from trainer to inference process using Ray.

    This test verifies that the NCCLWeightTransferEngine can receive
    tensors broadcast by a trainer process via NCCL.
    """
    ray.init(ignore_reinit_error=True)

    master_address = "127.0.0.1"
    master_port = get_open_port()
    world_size = 2  # 1 trainer + 1 inference worker

    # Tensor to transfer: 100x100 ones
    tensor_shape = [100, 100]
    tensor_dtype = "float32"

    # Start both tasks concurrently - Ray assigns GPUs automatically
    inference_future = inference_receive_tensor.remote(
        master_address, master_port, world_size, tensor_shape, tensor_dtype
    )
    trainer_future = trainer_broadcast_tensor.remote(
        master_address, master_port, world_size, tensor_shape, tensor_dtype
    )

    # Wait for both to complete
    trainer_result, result = ray.get([trainer_future, inference_future])

    assert trainer_result, "Trainer should complete successfully"
    assert result["success"], (
        f"Weight transfer failed. "
        f"Received shape: {result['received_shape']}, "
        f"Received sum: {result['received_sum']}"
    )