vllm.model_executor.model_loader.utils

def configure_quant_config(quant_config: QuantizationConfig,
                           model_class: type[nn.Module]):
    """
    Pass packed_modules_mapping by reference to quant_config so that
    quant_config can properly match fused modules

    Note that model attributes are passed by reference to quant_config,
    enabling them to be updated by model_class.__new__ (ex. chatglm, qwen)

    Once the `SupportsQuant` mixin has been added to all models, this
    function can be removed
    """
    if not issubclass(model_class, SupportsQuant):
        hf_to_vllm_mapper = getattr(model_class, "hf_to_vllm_mapper", None)
        packed_mapping = getattr(model_class, "packed_modules_mapping", None)

        # pass mappings by reference to quant_config
        if hf_to_vllm_mapper is not None:
            quant_config.apply_vllm_mapper(hf_to_vllm_mapper)
        if packed_mapping is not None:
            quant_config.packed_modules_mapping = packed_mapping

@contextmanager
def device_loading_context(module: torch.nn.Module,
                           target_device: torch.device):
    if target_device.type == "cpu":
        # If target is CPU, no need to move anything
        yield module
        return

    original_device_states: dict[str, torch.device] = {}

    # Store original device states and move parameters to GPU if they're on CPU
    for name, p in module.named_parameters():
        if p.device.type == "cpu":
            original_device_states[name] = p.device
            p.data = p.data.to(target_device)
        # Parameters already on target device are not touched

    try:
        yield module

    finally:
        # Restore parameters to their original devices, ignoring new parameters
        pin_memory = is_pin_memory_available()
        for name, p in module.named_parameters():
            if name in original_device_states:
                original_device: torch.device = original_device_states[name]
                if original_device.type == "cpu":
                    # `torch.empty_like` does not support `pin_memory` argument
                    cpu_data = torch.empty_strided(
                        size=p.data.size(),
                        stride=p.data.stride(),
                        dtype=p.data.dtype,
                        layout=p.data.layout,
                        device="cpu",
                        pin_memory=pin_memory,
                    )
                    cpu_data.copy_(p.data)
                    p.data = cpu_data
                else:
                    p.data = p.data.to(original_device)

def get_architecture_class_name(model_config: ModelConfig) -> str:
    return get_model_architecture(model_config)[1]

def get_model_architecture(
        model_config: ModelConfig) -> tuple[type[nn.Module], str]:
    architectures = getattr(model_config.hf_config, "architectures", [])

    # Special handling for quantized Mixtral.
    # FIXME(woosuk): This is a temporary hack.
    mixtral_supported = [
        "fp8",
        "compressed-tensors",
        "gptq_marlin",
        "awq_marlin",
        "quark",
        "bitsandbytes",
    ]

    if (model_config.quantization is not None
            and model_config.quantization not in mixtral_supported
            and "MixtralForCausalLM" in architectures):
        architectures = ["QuantMixtralForCausalLM"]

    model_cls, arch = model_config.registry.resolve_model_cls(
        architectures,
        model_config=model_config,
    )

    if arch == model_config._get_transformers_backend_cls():
        assert model_config.model_impl != ModelImpl.VLLM
        if model_config.model_impl == ModelImpl.AUTO:
            logger.warning_once(
                "%s has no vLLM implementation, falling back to Transformers "
                "implementation. Some features may not be supported and "
                "performance may not be optimal.", arch)

    convert_type = model_config.convert_type
    if convert_type == "none":
        pass
    elif convert_type == "embed":
        logger.debug_once("Converting to embedding model.")
        model_cls = as_embedding_model(model_cls)
    elif convert_type == "classify":
        logger.debug_once("Converting to sequence classification model.")
        model_cls = as_seq_cls_model(model_cls)
    elif convert_type == "reward":
        logger.debug_once("Converting to reward model.")
        model_cls = as_reward_model(model_cls)
    else:
        assert_never(convert_type)

    return model_cls, arch

def get_model_cls(model_config: ModelConfig) -> type[nn.Module]:
    return get_model_architecture(model_config)[0]

def initialize_model(
    vllm_config: VllmConfig,
    *,
    prefix: str = "",
    model_class: Optional[type[nn.Module]] = None,
    model_config: Optional[ModelConfig] = None,
) -> nn.Module:
    """Initialize a model with the given configurations."""
    if model_config is None:
        model_config = vllm_config.model_config
    if model_class is None:
        model_class, _ = get_model_architecture(model_config)

    if vllm_config.quant_config is not None:
        configure_quant_config(vllm_config.quant_config, model_class)

    signatures = inspect.signature(model_class.__init__)
    all_params = [param.name for param in signatures.parameters.values()]
    if "vllm_config" in all_params and "prefix" in all_params:
        # new-style model class
        with set_current_vllm_config(vllm_config,
                                     check_compile=True,
                                     prefix=prefix):
            return model_class(vllm_config=vllm_config, prefix=prefix)

    msg = ("vLLM model class should accept `vllm_config` and `prefix` as "
           "input arguments. Possibly you have an old-style model class"
           " registered from out of tree and it is used for new vLLM version. "
           "Check https://docs.vllm.ai/en/latest/design/arch_overview.html "
           "for the design and update the model class accordingly.")
    warnings.warn(msg, DeprecationWarning, stacklevel=2)

    logger.warning(
        "Trying to guess the arguments for old-style model class %s",
        model_class,
    )
    # try to be compatible with old-style model class
    kwargs = {}
    if "prefix" in all_params:
        kwargs["prefix"] = prefix
    if "config" in all_params:
        kwargs["config"] = model_config.hf_config
    if "cache_config" in all_params:
        kwargs["cache_config"] = vllm_config.cache_config
    if "quant_config" in all_params:
        kwargs["quant_config"] = vllm_config.quant_config
    if "lora_config" in all_params:
        kwargs["lora_config"] = vllm_config.lora_config
    if "scheduler_config" in all_params:
        kwargs["scheduler_config"] = vllm_config.scheduler_config
    with set_current_vllm_config(vllm_config,
                                 check_compile=True,
                                 prefix=prefix):
        return model_class(**kwargs)

def process_weights_after_loading(model: nn.Module, model_config: ModelConfig,
                                  target_device: torch.device) -> None:
    for _, module in model.named_modules():
        if isinstance(module, QKVCrossParallelLinear):
            # NOTE(Isotr0py): special case for cross QKV layer because
            # q and kv proj aren't registered as submodules intentionally
            module.process_weights_after_loading()
            continue
        quant_method = getattr(module, "quant_method", None)
        if isinstance(quant_method, QuantizeMethodBase):
            # When quant methods need to process weights after loading
            # (for repacking, quantizing, etc), they expect parameters
            # to be on the global target device. This scope is for the
            # case where cpu offloading is used, where we will move the
            # parameters onto device for processing and back off after.
            with device_loading_context(module, target_device):
                quant_method.process_weights_after_loading(module)

    # Currently only used by MLA.
    # NOTE: This intentionally happens after other modules so we can easily
    # decompress the weights for MLA.
    for _, module in model.named_modules():
        if isinstance(module, Attention) and \
            hasattr(module, "process_weights_after_loading"):
            # TODO(lucas): see if there is a way to unify the signatures
            # of process_weights_after_loading
            module.process_weights_after_loading(model_config.dtype)

@contextlib.contextmanager
def set_default_torch_dtype(dtype: torch.dtype):
    """Sets the default torch dtype to the given dtype."""
    old_dtype = torch.get_default_dtype()
    torch.set_default_dtype(dtype)
    yield
    torch.set_default_dtype(old_dtype)