fluke.server

The module fluke.server provides the base classes for the servers in fluke.

Classes

class fluke.server.Server

aggregate	Aggregate the models of the clients.
broadcast_model	Broadcast the global model to the clients.
channel	The channel to communicate with the clients.
evaluate	Evaluate the global federated model on the test_set.
finalize	Finalize the federated learning process.
fit	Run the federated learning algorithm.
get_eligible_clients	Get the clients that will participate in the current round.
has_test	Return whether the server can evaluate the model.
has_model	Return whether the server owns a global model.
load	Load the server's state from file.
receive_client_models	Retrieve the models of the clients.
save	Save the server's state to file.
state_dict	Return the server's state as a dictionary.
_get_client_weights	Get the weights of the clients for the aggregation.

class fluke.server.Server(model: torch.nn.Module, test_set: FastDataLoader, clients: Iterable[Client], weighted: bool = False, lr: float = 1.0, **kwargs: dict[str, Any])

Basic Server for Federated Learning.

This class is the base class for all servers in fluke. It implements the basic functionalities of a federated learning server. The default behaviour of this server is based on the Federated Averaging algorithm. The server is responsible for coordinating the learning process, selecting the clients for each round, sending the global model to the clients, and aggregating the models received from the clients at the end of the round. The server also evaluates the model server-side (if the test data is provided).

hyper_params

The hyper-parameters of the server. The default hyper-parameters are:

• weighted: A boolean indicating if the clients should be weighted by the number of samples when aggregating the models.

When a new server class inherits from this class, it must add all its hyper-parameters to this dictionary.

Type:

DDict

device

The device where the server runs.

Type:

torch.device

model

The federated model to be trained.

Type:

torch.nn.Module

clients

The clients that will participate in the federated learning process.

Type:

Iterable[Client]

n_clients

The number of clients that will participate in the federated learning

Type:

int

rounds

The number of rounds that have been executed.

Type:

int

test_set

The test data to evaluate the model. If None, the model will not be evaluated server-side.

Type:

FastDataLoader

Parameters:

• model (torch.nn.Module) – The federated model to be trained.

• test_set (FastDataLoader) – The test data to evaluate the model.

• clients (Iterable[Client]) – The clients that will participate in the federated learning process.

• weighted (bool) – A boolean indicating if the clients should be weighted by the number of samples when aggregating the models. Defaults to False.

_get_client_weights(eligible: Iterable[Client]) → list[float]

Get the weights of the clients for the aggregation. The weights are calculated based on the number of samples of each client. If the hyperparameter weighted is True, the clients are weighted by their number of samples. Otherwise, all clients have the same weight.

Caution

The computation of the weights do not adhere to the “best-practices” of fluke because the server should not have direct access to the number of samples of the clients. Thus, the computation of the weights should be done communicating with the clients through the channel but, for simplicity, we are not following this practice here. However, the communication overhead is negligible and does not affect the logged performance.

Parameters:

eligible (Iterable[Client]) – The clients that will participate in the aggregation.

Returns:

The weights of the clients.

Return type:

list[float]

aggregate(eligible: Iterable[Client], client_models: Iterable[torch.nn.Module]) → None

Aggregate the models of the clients. The aggregation is done by averaging the models of the clients. If the hyperparameter weighted is True, the clients are weighted by their number of samples. The method directly updates the model of the server. Formally, let \(\theta\) be the model of the server, \(\theta_i\) the model of client \(i\), and \(w_i\) the weight of client \(i\) such that \(\sum_{i=1}^{N} w_i = 1\). The aggregation is done as follows [FedAVG]:

\[\theta = \sum_{i=1}^{N} w_i \theta_i\]

Note

In case of networks with batch normalization layers, the running statistics of the batch normalization layers are also aggregated. For all statistics but num_batches_tracked are aggregated the mean is computed, while for the num_batches_tracked parameter, the maximum between the clients’ values is taken.

See also

fluke.utils.model.aggregate_models()

Parameters:

• eligible (Iterable[Client]) – The clients that will participate in the aggregation.

• client_models (Iterable[torch.nn.Module]) – The models of the clients.

References

[FedAVG]

H. B. McMahan, E. Moore, D. Ramage, S. Hampson, and B. A. y Arcas, “Communication-Efficient Learning of Deep Networks from Decentralized Data”. In AISTATS (2017).

broadcast_model(eligible: Iterable[Client]) → None

Broadcast the global model to the clients.

Parameters:

eligible (Iterable[Client]) – The clients that will receive the global model.

property channel: Channel

The channel to communicate with the clients.

Important

Always use this channel to exchange data/information with the clients. The server should directly call the clients’ methods only to trigger specific actions.

Returns:

The channel to communicate with the clients.

Return type:

Channel

evaluate(evaluator: Evaluator, test_set: FastDataLoader) → dict[str, float]

Evaluate the global federated model on the test_set. If the test set is not set, the method returns an empty dictionary.

Returns:

The evaluation results. The keys are the metrics and the values are

the results.

Return type:

dict[str, float]

finalize() → None

Finalize the federated learning process. The finalize method is called at the end of the federated learning process. The client-side evaluation is only done if the client has participated in at least one round.

fit(n_rounds: int = 10, eligible_perc: float = 0.1, finalize: bool = True, **kwargs: dict[str, Any]) → None

Run the federated learning algorithm. The default behaviour of this method is to run the Federated Averaging algorithm. The server selects a percentage of the clients to participate in each round, sends the global model to the clients, which compute the local updates and send them back to the server. The server aggregates the models of the clients and repeats the process for a number of rounds.

Parameters:

• n_rounds (int, optional) – The number of rounds to run. Defaults to 10.

• eligible_perc (float, optional) – The percentage of clients that will be selected for each round. Defaults to 0.1.

• finalize (bool, optional) – If True, the server will finalize the federated learning process. Defaults to True.

• **kwargs – Additional keyword arguments.

get_eligible_clients(eligible_perc: float) → Iterable[Client]

Get the clients that will participate in the current round. Clients are selected randomly based on the percentage of eligible clients.

Parameters:

eligible_perc (float) – The percentage of clients that will be selected.

Returns:

The clients that will participate in the current round.

Return type:

Iterable[Client]

property has_model: bool

Return whether the server owns a global model.

Returns:

True if the server owns a global model, False otherwise.

Return type:

bool

property has_test: bool

Return whether the server can evaluate the model.

Returns:

True if the server can evaluate the model, False otherwise.

Return type:

bool

load(path: str) → None

Load the server’s state from file.

Parameters:

path (str) – The path to load the server’s state.

receive_client_models(eligible: Iterable[Client], state_dict: bool = True) → Generator[torch.nn.Module, None, None]

Retrieve the models of the clients. This method assumes that the clients have already sent their models to the server. The models are received through the channel in the same order as the clients in eligible.

Caution

The method returns a generator of the models of the clients to avoid to clutter the memory with all the models. This means that this method is expected to be called only once per round. If the models are needed multiple times, the generator should be converted to a list, tuple, or any other iterable.

Parameters:

• eligible (Iterable[Client]) – The clients that will participate in the aggregation.

• state_dict (bool, optional) – If True, the method returns the state_dict of the models. Otherwise, it returns the models. Defaults to True.

Returns:

The models of the clients.

Return type:

Generator[torch.nn.Module]

save(path: str) → None

Save the server’s state to file.

Parameters:

path (str) – The path to save the server.

state_dict() → dict

Return the server’s state as a dictionary.

Returns:

The server’s state.

Return type:

dict