Experiments

Running the experiment

This is an example of an experimental study based on solving three problems of the ZDT family with three different algorithms: NSGA-II, GDE3 and SMPSO.

The hypervolume, generational distance and epsilon indicators are used for performance assessment.

from jmetal.algorithm.multiobjective.gde3 import GDE3
from jmetal.algorithm.multiobjective.nsgaii import NSGAII
from jmetal.algorithm.multiobjective.smpso import SMPSO
from jmetal.core.quality_indicator import *
from jmetal.lab.experiment import Experiment, Job, generate_summary_from_experiment
from jmetal.operator import PolynomialMutation, SBXCrossover
from jmetal.problem import ZDT1, ZDT2, ZDT3
from jmetal.util.archive import CrowdingDistanceArchive
from jmetal.util.termination_criterion import StoppingByEvaluations


def configure_experiment(problems: dict, n_run: int):
    jobs = []
    max_evaluations = 25000

    for run in range(n_run):
        for problem_tag, problem in problems.items():
            jobs.append(
                Job(
                    algorithm=NSGAII(
                        problem=problem,
                        population_size=100,
                        offspring_population_size=100,
                        mutation=PolynomialMutation(probability=1.0 / problem.number_of_variables,
                                                    distribution_index=20),
                        crossover=SBXCrossover(probability=1.0, distribution_index=20),
                        termination_criterion=StoppingByEvaluations(max=max_evaluations)
                    ),
                    algorithm_tag='NSGAII',
                    problem_tag=problem_tag,
                    run=run,
                )
            )
            jobs.append(
                Job(
                    algorithm=GDE3(
                        problem=problem,
                        population_size=100,
                        cr=0.5,
                        f=0.5,
                        termination_criterion=StoppingByEvaluations(max=max_evaluations)
                    ),
                    algorithm_tag='GDE3',
                    problem_tag=problem_tag,
                    run=run,
                )
            )
            jobs.append(
                Job(
                    algorithm=SMPSO(
                        problem=problem,
                        swarm_size=100,
                        mutation=PolynomialMutation(probability=1.0 / problem.number_of_variables,
                                                    distribution_index=20),
                        leaders=CrowdingDistanceArchive(100),
                        termination_criterion=StoppingByEvaluations(max=max_evaluations)
                    ),
                    algorithm_tag='SMPSO',
                    problem_tag=problem_tag,
                    run=run,
                )
            )

    return jobs


if __name__ == '__main__':
    # Configure the experiments
    jobs = configure_experiment(problems={'ZDT1': ZDT1(), 'ZDT2': ZDT2(), 'ZDT3': ZDT3()}, n_run=31)

    # Run the study
    output_directory = 'data'
    experiment = Experiment(output_dir=output_directory, jobs=jobs)
    experiment.run()

Summary file

The results of this experiment can be summarized to a CSV file as follows:

if __name__ == '__main__':
    # experiment = ...

    # Generate summary file
    generate_summary_from_experiment(
        input_dir=output_directory,
        reference_fronts='/home/user/jMetalPy/resources/reference_front',
        quality_indicators=[GenerationalDistance(), EpsilonIndicator(), HyperVolume([1.0, 1.0])]
    )

This file contains all the information of the quality indicator values, for each configuration and run. The summary file is the input of all the statistical tests, so that they can be applied to any valid file having the proper format.

$ head QualityIndicatorSummary.csv
Algorithm,Problem,IndicatorName,ExecutionId,IndicatorValue
NSGAII,ZDT1,EP,0,0.015705992620067832
NSGAII,ZDT1,EP,1,0.012832504015918067
...

API

class jmetal.lab.experiment.Experiment(output_dir: str, jobs: List[jmetal.lab.experiment.Job], m_workers: int = 6)

Bases: object

run() → None

class jmetal.lab.experiment.Job(algorithm: jmetal.core.algorithm.Algorithm, algorithm_tag: str, problem_tag: str, run: int)

Bases: object

execute(output_path: str = '')

jmetal.lab.experiment.generate_summary_from_experiment(input_dir: str, quality_indicators: List[jmetal.core.quality_indicator.QualityIndicator], reference_fronts: str = '')

Compute a list of quality indicators. The input data directory must met the following structure (this is generated automatically by the Experiment class):

• <base_dir>

  • algorithm_a

    • problem_a

      • FUN.0.tsv

      • FUN.1.tsv

      • VAR.0.tsv

      • VAR.1.tsv

      • …

Parameters

• input_dir – Directory where all the input data is found (function values and variables).

• reference_fronts – Directory where reference fronts are found.

• quality_indicators – List of quality indicators to compute.

Returns

None.