fairlearn.adversarial.AdversarialFairnessClassifier#

class fairlearn.adversarial.AdversarialFairnessClassifier(*, backend='auto', predictor_model=None, adversary_model=None, predictor_optimizer='Adam', adversary_optimizer='Adam', constraints='demographic_parity', learning_rate=0.001, alpha=1.0, epochs=1, batch_size=32, shuffle=False, progress_updates=None, skip_validation=False, callbacks=None, cuda=None, warm_start=False, random_state=None)[source]#

Train PyTorch or TensorFlow classifiers while mitigating unfairness.

This estimator implements the supervised learning method proposed in “Mitigating Unwanted Biases with Adversarial Learning”. [1] The training algorithm takes as input two neural network models, a predictor model and an adversarial model, defined either as a PyTorch module or TensorFlow2 model. The API follows conventions of sklearn estimators.

The predictor model takes the features X as input and seeks to predict y. For binary classification, the predictor model should return a single real-valued score, which is transformed into a probability of the positive class via the logistic function (aka sigmoid), similarly to logistic regression. For multi-class classification, the predictor model should return a vector of real-valued scores, which are transformed into class probabilities via the softmax function, similarly to multinomial logistic regression. The training loss is the negative log likelihood (aka log loss, logistic loss, cross-entropy loss).

The adversarial model for demographic parity takes scores produced by the predictor model as input, and seeks to predict sensitive_features. Depending on the type of the provided sensitive features, the model should produce a scalar or vector output. Three types of sensitive features are supported: (1) a single binary feature; (2) a single discrete feature; (3) one or multiple real-valued features. For a single binary sensitive feature and a single discrete feature, the network outputs are transformed by the logistic function and the softmax function, respectively, and the loss is the negative log likelihood. For one or multiple real-valued features, the network output is left as is, and the loss is a square loss.

The adversarial model for equalized odds additionaly takes y as input. For multi-class classification, y is transformed using one-hot encoding.

Parameters:
backendstr, BackendEngine, default = ‘auto’

The backend to use. Must be one of 'torch', 'tensorflow', or 'auto' which indicates PyTorch, TensorFlow, or to automatically infer the backend from the predictor_model. You can also pass in a BackendEngine class.

predictor_modellist, torch.nn.Module, keras.Model

The predictor model to train. Instead of a neural network model, it is possible to pass a list \([k_1, k_2, \dots]\), where each \(k_i\) either indicates the number of nodes (if \(k_i\) is an integer) or an activation function (if \(k_i\) is a string) or a layer or activation function instance directly (if \(k_i\) is a callable). The default parameter is [], which indicates a neural network without any hidden layers. However, the number of nodes in the input and output layer are automatically inferred from data, and the final activation function (such as softmax for categorical predictors) are inferred from data. If backend is specified, you cannot pass a model that uses a different backend.

adversary_modellist, torch.nn.Module, keras.Model

The adversary model to train. Defined similarly as predictor_model. Must be the same type as the predictor_model.

predictor_optimizerstr, torch.optim, keras.optimizers, callable, default = ‘Adam’

The optimizer class to use. If a string is passed instead, this must be either ‘SGD’ or ‘Adam’. A corresponding SGD or Adam optimizer is initialized with the given predictor model and learning rate. If an instance of a subclass of torch.optim.Optimizer or keras.optimizers.Optimizer is passed, this is used directly. If a callable fn is passed, we call this callable and pass our model, and set the result of this call as the optimizer, so: predictor_optimizer=fn(predictor_model).

adversary_optimizerstr, torch.optim, keras.optimizers, callable, default = ‘Adam’

The optimizer class to use. Defined similarly as predictor_optimizer.

constraintsstr, default = ‘demographic_parity’

The fairness constraint. Must be either ‘demographic_parity’ or ‘equalized_odds’.

learning_ratefloat, default = 0.001

A small number greater than zero to set as a learning rate.

alphafloat, default = 1.0

A small number \(\alpha\) as specified in the paper. It is the factor that balances the training towards predicting y (choose \(\alpha\) closer to zero) or enforcing fairness constraint (choose larger \(\alpha\)).

epochsint, default = 1

Number of epochs to train for.

batch_sizeint, default = 32

Batch size. For no batching, set this to -1.

shufflebool, default = False

When true, shuffle the data before every epoch (including the first).

progress_updatesnumber, optional, default = None

If a number \(t\) is provided, we print an update about the training loop after processing a batch and \(t\) seconds have passed since the previous update.

skip_validationbool, default = False

Skip the validation of the data. Useful because validate_input is a costly operation, and we may instead pass all data to validate_input at an earlier stage. Note that not only checking X is skipped, but also no tranform is applied to y and sensitive_features.

callbackscallable

Callback function, called after every batch. For instance useable when wanting to validate. A list of callback functions can also be provided. Each callback function is called as:

callback(
    self, step=self.step_, X=X, y=y, z=sensitive_features, pos_label=1
)

which is passed the self object, the step number, the inputs X, the targets y, the sensitive features z, and the positive label. The callback may return a Boolean value. If the returned value is True, the optimization algorithm terminates. This can be used to implement early stopping.

cudastr, default = None

A string to indicate which device to use when training. For instance, set cuda='cuda:0' to train on the first GPU. Only for PyTorch backend.

warm_startbool, default = False

Normally, when set to False, a call to fit() triggers reinitialization, which discards the models and intializes them again. Setting to True triggers reuse of these models. Note: if pre-initialized models are passed, the models (and their parameters) are never discarded.

random_stateint, RandomState, default = None

Controls the randomized aspects of this algorithm, such as shuffling. Useful to get reproducible output across multiple function calls.

References

fit(X, y, *, sensitive_features=None)[source]#

Fit the model based on the given training data and sensitive features.

Currently, for discrete y and sensitive_features ALL classes need to be passed in the first call to fit!

Parameters:
Xnumpy.ndarray

Two-dimensional numpy array containing training data

yarray

Array-like containing training targets

sensitive_featuresarray

Array-like containing the sensitive features of the training data.

get_metadata_routing()[source]#

Get metadata routing of this object.

Please check User Guide on how the routing mechanism works.

Returns:
routingMetadataRequest

A MetadataRequest encapsulating routing information.

get_params(deep=True)[source]#

Get parameters for this estimator.

Parameters:
deepbool, default=True

If True, will return the parameters for this estimator and contained subobjects that are estimators.

Returns:
paramsdict

Parameter names mapped to their values.

partial_fit(X, y, *, classes=None, sensitive_features=None)[source]#

Perform one training step on given samples and update model.

This method allows for incremental fitting on batches of data.

Parameters:
Xarray-like of shape (n_samples, n_features)

The training input samples.

yarray-like of shape (n_samples,)

The target values.

classesarray-like of shape (n_classes,), default=None

List of all the classes that can possibly appear in the y vector. Must be provided at the first call to partial_fit, can be omitted in subsequent calls.

sensitive_featuresarray-like of shape (n_samples,), default=None

The sensitive features for each sample. If None, a vector of zeros will be used.

Returns:
selfobject

Returns self.

predict(X)[source]#

Compute predictions for given test data.

Predictions are discrete for classifiers, making use of the predictor_function.

Parameters:
Xnumpy.ndarray

Two-dimensional numpy array containing test data

Returns:
y_predarray

array-like containing the model’s predictions fed through the (discrete) predictor_function

score(X, y, sample_weight=None)[source]#

Return the mean accuracy on the given test data and labels.

In multi-label classification, this is the subset accuracy which is a harsh metric since you require for each sample that each label set be correctly predicted.

Parameters:
Xarray-like of shape (n_samples, n_features)

Test samples.

yarray-like of shape (n_samples,) or (n_samples, n_outputs)

True labels for X.

sample_weightarray-like of shape (n_samples,), default=None

Sample weights.

Returns:
scorefloat

Mean accuracy of self.predict(X) w.r.t. y.

set_fit_request(*, sensitive_features: bool | None | str = '$UNCHANGED$') → AdversarialFairnessClassifier[source]#

Request metadata passed to the fit method.

Note that this method is only relevant if enable_metadata_routing=True (see sklearn.set_config()). Please see User Guide on how the routing mechanism works.

The options for each parameter are:

  • True: metadata is requested, and passed to fit if provided. The request is ignored if metadata is not provided.

  • False: metadata is not requested and the meta-estimator will not pass it to fit.

  • None: metadata is not requested, and the meta-estimator will raise an error if the user provides it.

  • str: metadata should be passed to the meta-estimator with this given alias instead of the original name.

The default (sklearn.utils.metadata_routing.UNCHANGED) retains the existing request. This allows you to change the request for some parameters and not others.

New in version 1.3.

Note

This method is only relevant if this estimator is used as a sub-estimator of a meta-estimator, e.g. used inside a Pipeline. Otherwise it has no effect.

Parameters:
sensitive_featuresstr, True, False, or None, default=sklearn.utils.metadata_routing.UNCHANGED

Metadata routing for sensitive_features parameter in fit.

Returns:
selfobject

The updated object.

set_params(**params)[source]#

Set the parameters of this estimator.

The method works on simple estimators as well as on nested objects (such as Pipeline). The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.

Parameters:
**paramsdict

Estimator parameters.

Returns:
selfestimator instance

Estimator instance.

set_partial_fit_request(*, classes: bool | None | str = '$UNCHANGED$', sensitive_features: bool | None | str = '$UNCHANGED$') → AdversarialFairnessClassifier[source]#

Request metadata passed to the partial_fit method.

Note that this method is only relevant if enable_metadata_routing=True (see sklearn.set_config()). Please see User Guide on how the routing mechanism works.

The options for each parameter are:

  • True: metadata is requested, and passed to partial_fit if provided. The request is ignored if metadata is not provided.

  • False: metadata is not requested and the meta-estimator will not pass it to partial_fit.

  • None: metadata is not requested, and the meta-estimator will raise an error if the user provides it.

  • str: metadata should be passed to the meta-estimator with this given alias instead of the original name.

The default (sklearn.utils.metadata_routing.UNCHANGED) retains the existing request. This allows you to change the request for some parameters and not others.

New in version 1.3.

Note

This method is only relevant if this estimator is used as a sub-estimator of a meta-estimator, e.g. used inside a Pipeline. Otherwise it has no effect.

Parameters:
classesstr, True, False, or None, default=sklearn.utils.metadata_routing.UNCHANGED

Metadata routing for classes parameter in partial_fit.

sensitive_featuresstr, True, False, or None, default=sklearn.utils.metadata_routing.UNCHANGED

Metadata routing for sensitive_features parameter in partial_fit.

Returns:
selfobject

The updated object.

set_score_request(*, sample_weight: bool | None | str = '$UNCHANGED$') → AdversarialFairnessClassifier[source]#

Request metadata passed to the score method.

Note that this method is only relevant if enable_metadata_routing=True (see sklearn.set_config()). Please see User Guide on how the routing mechanism works.

The options for each parameter are:

  • True: metadata is requested, and passed to score if provided. The request is ignored if metadata is not provided.

  • False: metadata is not requested and the meta-estimator will not pass it to score.

  • None: metadata is not requested, and the meta-estimator will raise an error if the user provides it.

  • str: metadata should be passed to the meta-estimator with this given alias instead of the original name.

The default (sklearn.utils.metadata_routing.UNCHANGED) retains the existing request. This allows you to change the request for some parameters and not others.

New in version 1.3.

Note

This method is only relevant if this estimator is used as a sub-estimator of a meta-estimator, e.g. used inside a Pipeline. Otherwise it has no effect.

Parameters:
sample_weightstr, True, False, or None, default=sklearn.utils.metadata_routing.UNCHANGED

Metadata routing for sample_weight parameter in score.

Returns:
selfobject

The updated object.