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Model Recombination

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Credit to FedMR

Usage

ModelRecombinationAlgorithm is a class used to recombine models in a model pool. Here's how to use it:

First, import the necessary modules:

from fusion_bench.method import ModelRecombinationAlgorithm
from fusion_bench.modelpool import ModelPool, to_modelpool
from torch import nn

Create an instance of ModelRecombinationAlgorithm:

model_recombination = ModelRecombinationAlgorithm()

Create a model pool using the to_modelpool function. This function takes a list of models or a dict of models and converts it into a ModelPool:

models = [nn.Linear(10, 10) for _ in range(3)]
modelpool = to_modelpool(models)

Use the run method of the ModelRecombinationAlgorithm instance to recombine the models in the model pool:

new_modelpool = model_recombination.run(modelpool, return_modelpool=True)

The run method takes two arguments:

  • modelpool: The model pool to recombine.
  • return_modelpool (optional): A boolean indicating whether to return the entire model pool or just the first model. Defaults to True.

If return_modelpool is True, the run method returns a new ModelPool with the recombined models. If False, it returns the first model from the new model pool.

new_model = model_recombination.run(modelpool, return_modelpool=False)

You can check the type of the returned value to ensure that the run method worked correctly:

assert isinstance(new_modelpool, ModelPool)
assert isinstance(new_model, nn.Module)

Code Integration

Configuration template for the model recombination algorithm:

config/method/model_recombination.yaml
name: model_recombination
# if `return_model_pool` is not null, the argument `return_modelpool` passed to the `run` method will be ignored.
return_modelpool: null

Construct a model recombination using our CLI tool fusion_bench:

fusion_bench \
    method=model_recombination \
        method.return_modelpool=false \
    modelpool=... \
    taskpool=...

References

ModelRecombinationAlgorithm

Bases: ModelFusionAlgorithm

Model recombination recombinates the layers of the given models, to create a new set of models.

Source code in fusion_bench/method/model_recombination.py 
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class ModelRecombinationAlgorithm(ModelFusionAlgorithm):
    """
    Model recombination recombinates the layers of the given models, to create a new set of models.
    """

    @torch.no_grad()
    def run(
        self,
        modelpool: ModelPool,
        return_modelpool: bool = True,
    ) -> Union[nn.Module, ModelPool]:
        """
        Executes the model recombination algorithm on a given model pool.

        This method loads models from the model pool, determines their type, and applies the appropriate recombination method.
        It then creates a new model pool with the recombined models. Depending on the `return_modelpool` flag, it either returns
        the entire new model pool or just the first model from it.

        - If the models in the model pool are of type `nn.ModuleList`, the recombination method `recombine_modellist` is used. Where each module in the list is shuffled across the models.
        - If the models are of type `nn.ModuleDict`, the recombination method `recombine_modeldict` is used. Where each module in the dictionary is shuffled across the models.
        - If the models are of type `nn.Module`, the recombination method `recombine_state_dict` is used. Where the state dictionaries of the models are shuffled across the models.

        Args:
            modelpool (ModelPool): The pool of models to recombine.
            return_modelpool (bool, optional): Flag indicating whether to return the entire model pool or just the first model. Defaults to True. If this algorithm is initialized with config, the value of `return_modelpool` in the config will be used and this argument passed to the method will be ignored.

        Returns:
            Union[nn.Module, ModelPool]: The recombined model pool or the first model from the recombined pool, depending on the `return_modelpool` flag.

        Raises:
            ValueError: If the models in the model pool are of an unsupported type.
        """
        # If the config has a return_modelpool flag, use that, otherwise use the argument
        if self.config.get("return_modelpool", None) is not None:
            return_modelpool = self.config.return_modelpool
        # check the modelpool type
        modelpool = to_modelpool(modelpool)

        log.info(f"Running model recombination algorithm with {len(modelpool)} models")

        # TODO: optimize the `recombine_*` functions, if `return_modelpool` is False, we don't need to create the new modelpool, just the first model
        models = [modelpool.load_model(m) for m in modelpool.model_names]
        if isinstance(models[0], nn.ModuleList):
            new_models = recombine_modellist(models)
        elif isinstance(models[0], nn.ModuleDict):
            new_models = recombine_modeldict(models)
        elif isinstance(models[0], nn.Module):
            new_models = recombine_state_dict(models)
        else:
            raise ValueError(f"Unsupported model type {type(models[0])}")

        new_modelpool = DictModelPool(
            {n: m for n, m in zip(modelpool.model_names, new_models)}
        )
        if return_modelpool:
            return new_modelpool
        else:
            return new_modelpool.load_model(new_modelpool.model_names[0])
run(modelpool, return_modelpool=True)

Executes the model recombination algorithm on a given model pool.

This method loads models from the model pool, determines their type, and applies the appropriate recombination method. It then creates a new model pool with the recombined models. Depending on the return_modelpool flag, it either returns the entire new model pool or just the first model from it.

  • If the models in the model pool are of type nn.ModuleList, the recombination method recombine_modellist is used. Where each module in the list is shuffled across the models.
  • If the models are of type nn.ModuleDict, the recombination method recombine_modeldict is used. Where each module in the dictionary is shuffled across the models.
  • If the models are of type nn.Module, the recombination method recombine_state_dict is used. Where the state dictionaries of the models are shuffled across the models.

Parameters:

  • modelpool (ModelPool) –

    The pool of models to recombine.

  • return_modelpool (bool, default: True ) –

    Flag indicating whether to return the entire model pool or just the first model. Defaults to True. If this algorithm is initialized with config, the value of return_modelpool in the config will be used and this argument passed to the method will be ignored.

Returns:

  • Union[Module, ModelPool] –

    Union[nn.Module, ModelPool]: The recombined model pool or the first model from the recombined pool, depending on the return_modelpool flag.

Raises:

  • ValueError –

    If the models in the model pool are of an unsupported type.

Source code in fusion_bench/method/model_recombination.py 
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@torch.no_grad()
def run(
    self,
    modelpool: ModelPool,
    return_modelpool: bool = True,
) -> Union[nn.Module, ModelPool]:
    """
    Executes the model recombination algorithm on a given model pool.

    This method loads models from the model pool, determines their type, and applies the appropriate recombination method.
    It then creates a new model pool with the recombined models. Depending on the `return_modelpool` flag, it either returns
    the entire new model pool or just the first model from it.

    - If the models in the model pool are of type `nn.ModuleList`, the recombination method `recombine_modellist` is used. Where each module in the list is shuffled across the models.
    - If the models are of type `nn.ModuleDict`, the recombination method `recombine_modeldict` is used. Where each module in the dictionary is shuffled across the models.
    - If the models are of type `nn.Module`, the recombination method `recombine_state_dict` is used. Where the state dictionaries of the models are shuffled across the models.

    Args:
        modelpool (ModelPool): The pool of models to recombine.
        return_modelpool (bool, optional): Flag indicating whether to return the entire model pool or just the first model. Defaults to True. If this algorithm is initialized with config, the value of `return_modelpool` in the config will be used and this argument passed to the method will be ignored.

    Returns:
        Union[nn.Module, ModelPool]: The recombined model pool or the first model from the recombined pool, depending on the `return_modelpool` flag.

    Raises:
        ValueError: If the models in the model pool are of an unsupported type.
    """
    # If the config has a return_modelpool flag, use that, otherwise use the argument
    if self.config.get("return_modelpool", None) is not None:
        return_modelpool = self.config.return_modelpool
    # check the modelpool type
    modelpool = to_modelpool(modelpool)

    log.info(f"Running model recombination algorithm with {len(modelpool)} models")

    # TODO: optimize the `recombine_*` functions, if `return_modelpool` is False, we don't need to create the new modelpool, just the first model
    models = [modelpool.load_model(m) for m in modelpool.model_names]
    if isinstance(models[0], nn.ModuleList):
        new_models = recombine_modellist(models)
    elif isinstance(models[0], nn.ModuleDict):
        new_models = recombine_modeldict(models)
    elif isinstance(models[0], nn.Module):
        new_models = recombine_state_dict(models)
    else:
        raise ValueError(f"Unsupported model type {type(models[0])}")

    new_modelpool = DictModelPool(
        {n: m for n, m in zip(modelpool.model_names, new_models)}
    )
    if return_modelpool:
        return new_modelpool
    else:
        return new_modelpool.load_model(new_modelpool.model_names[0])

recombine_modellist(models)

Source code in fusion_bench/method/model_recombination.py 
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def recombine_modellist(models: List[nn.ModuleList]):
    num_models = len(models)
    num_layers = len(models[0])

    new_models = [[] for _ in range(num_models)]
    for layer_idx in range(num_layers):
        shuffled_layers = [m[layer_idx] for m in models]
        random.shuffle(shuffled_layers)
        for model_idx in range(num_models):
            new_models[model_idx].append(shuffled_layers[model_idx])
    new_models = [nn.ModuleList(m) for m in new_models]
    return new_models

recombine_modeldict(models)

Source code in fusion_bench/method/model_recombination.py 
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def recombine_modeldict(models: List[nn.ModuleDict]):
    num_models = len(models)

    new_models = [{} for _ in range(num_models)]
    for layer_name in models[0].keys():
        shuffled_layers = [m[layer_name] for m in models]
        random.shuffle(shuffled_layers)
        for model_idx in range(num_models):
            new_models[model_idx][layer_name] = shuffled_layers[model_idx]
    new_models = [nn.ModuleDict(m) for m in new_models]
    return new_models

recombine_state_dict(models)

Source code in fusion_bench/method/model_recombination.py 
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def recombine_state_dict(models: List[nn.Module]):
    num_models = len(models)
    state_dicts = [model.state_dict() for model in models]
    new_state_dict = [{} for _ in range(num_models)]
    for key in state_dicts[0].keys():
        shuffled_layers = [state_dict[key] for state_dict in state_dicts]
        random.shuffle(shuffled_layers)
        for model_idx in range(num_models):
            new_state_dict[model_idx][key] = shuffled_layers[model_idx]
    for model_idx in range(num_models):
        models[model_idx].load_state_dict(new_state_dict[model_idx])
    return models