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"""NSGA-II multi-objective optimizer.""" |
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# copyright: hyperactive developers, MIT License (see LICENSE file) |
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from .._adapters._base_optuna_adapter import _BaseOptunaAdapter |
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class NSGAIIOptimizer(_BaseOptunaAdapter): |
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"""NSGA-II multi-objective optimizer. |
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Parameters |
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---------- |
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param_space : dict[str, tuple or list or optuna distributions] |
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The search space to explore. Dictionary with parameter names |
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as keys and either tuples/lists of (low, high) or |
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optuna distribution objects as values. |
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n_trials : int, default=100 |
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Number of optimization trials. |
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initialize : dict[str, int], default=None |
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The method to generate initial positions. A dictionary with |
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the following key literals and the corresponding value type: |
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{"grid": int, "vertices": int, "random": int, "warm_start": list[dict]} |
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random_state : None, int, default=None |
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If None, create a new random state. If int, create a new random state |
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seeded with the value. |
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early_stopping : int, default=None |
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Number of trials after which to stop if no improvement. |
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max_score : float, default=None |
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Maximum score threshold. Stop optimization when reached. |
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population_size : int, default=50 |
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Population size for NSGA-II. |
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mutation_prob : float, default=0.1 |
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Mutation probability for NSGA-II. |
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crossover_prob : float, default=0.9 |
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Crossover probability for NSGA-II. |
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experiment : BaseExperiment, optional |
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The experiment to optimize parameters for. |
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Optional, can be passed later via ``set_params``. |
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Examples |
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-------- |
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Basic usage of NSGAIIOptimizer with a scikit-learn experiment: |
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>>> from hyperactive.experiment.integrations import SklearnCvExperiment |
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>>> from hyperactive.opt.optuna import NSGAIIOptimizer |
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>>> from sklearn.datasets import load_iris |
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>>> from sklearn.svm import SVC |
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>>> X, y = load_iris(return_X_y=True) |
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>>> sklearn_exp = SklearnCvExperiment(estimator=SVC(), X=X, y=y) |
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>>> param_space = { |
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... "C": (0.01, 10), |
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... "gamma": (0.0001, 10), |
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... } |
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>>> optimizer = NSGAIIOptimizer( |
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... param_space=param_space, n_trials=50, experiment=sklearn_exp |
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... ) |
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>>> best_params = optimizer.solve() |
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""" |
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_tags = { |
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"info:name": "NSGA-II Optimizer", |
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"info:local_vs_global": "global", |
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"info:explore_vs_exploit": "mixed", |
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"info:compute": "high", |
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"python_dependencies": ["optuna"], |
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} |
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def __init__( |
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self, |
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param_space=None, |
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n_trials=100, |
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initialize=None, |
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random_state=None, |
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early_stopping=None, |
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max_score=None, |
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population_size=50, |
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mutation_prob=0.1, |
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crossover_prob=0.9, |
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experiment=None, |
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): |
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self.population_size = population_size |
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self.mutation_prob = mutation_prob |
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self.crossover_prob = crossover_prob |
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super().__init__( |
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param_space=param_space, |
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n_trials=n_trials, |
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initialize=initialize, |
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random_state=random_state, |
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early_stopping=early_stopping, |
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max_score=max_score, |
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experiment=experiment, |
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) |
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def _get_optimizer(self): |
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"""Get the NSGA-II optimizer. |
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Returns |
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------- |
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optimizer |
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The Optuna NSGAIIOptimizer instance |
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""" |
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import optuna |
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optimizer_kwargs = { |
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"population_size": self.population_size, |
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"mutation_prob": self.mutation_prob, |
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"crossover_prob": self.crossover_prob, |
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} |
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if self.random_state is not None: |
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optimizer_kwargs["seed"] = self.random_state |
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return optuna.samplers.NSGAIISampler(**optimizer_kwargs) |
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View Code Duplication |
@classmethod |
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def get_test_params(cls, parameter_set="default"): |
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"""Return testing parameter settings for the optimizer.""" |
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from sklearn.datasets import load_iris |
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from sklearn.ensemble import RandomForestClassifier |
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from hyperactive.experiment.integrations import SklearnCvExperiment |
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# Test case 1: Basic single-objective (inherits from base) |
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params = super().get_test_params(parameter_set) |
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params[0].update( |
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{ |
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"population_size": 20, |
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"mutation_prob": 0.2, |
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"crossover_prob": 0.8, |
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} |
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) |
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# Test case 2: Multi-objective with mixed parameter types |
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X, y = load_iris(return_X_y=True) |
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rf_exp = SklearnCvExperiment( |
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estimator=RandomForestClassifier(random_state=42), X=X, y=y |
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) |
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mixed_param_space = { |
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"n_estimators": (10, 50), # Continuous integer |
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"max_depth": [3, 5, 7, None], # Mixed discrete/None |
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"criterion": ["gini", "entropy"], # Categorical |
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"min_samples_split": (2, 10), # Continuous integer |
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"bootstrap": [True, False], # Boolean categorical |
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} |
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params.append( |
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{ |
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"param_space": mixed_param_space, |
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"n_trials": 15, # Smaller for faster testing |
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"experiment": rf_exp, |
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"population_size": 8, # Smaller population for testing |
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"mutation_prob": 0.1, |
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"crossover_prob": 0.9, |
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} |
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) |
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return params |
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SimonBlanke /
Hyperactive
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