Source code for jmetal.algorithm.multiobjective.mocell

import copy
from functools import cmp_to_key
from typing import TypeVar, List

from jmetal.algorithm.singleobjective.genetic_algorithm import GeneticAlgorithm
from jmetal.config import store
from jmetal.core.operator import Mutation, Crossover, Selection
from jmetal.core.problem import Problem
from jmetal.operator import BinaryTournamentSelection
from jmetal.util.archive import BoundedArchive
from jmetal.util.density_estimator import CrowdingDistance, DensityEstimator
from jmetal.util.evaluator import Evaluator
from jmetal.util.generator import Generator
from jmetal.util.neighborhood import Neighborhood
from jmetal.util.ranking import FastNonDominatedRanking, Ranking
from jmetal.util.comparator import Comparator, MultiComparator
from jmetal.util.termination_criterion import TerminationCriterion

S = TypeVar('S')
R = TypeVar('R')

"""
.. module:: MOCell
   :platform: Unix, Windows
   :synopsis: MOCell (Multi-Objective Cellular evolutionary algorithm) implementation
.. moduleauthor:: Antonio J. Nebro <antonio@lcc.uma.es>
"""


[docs]class MOCell(GeneticAlgorithm[S, R]):

    def __init__(self,
                 problem: Problem,
                 population_size: int,
                 neighborhood: Neighborhood,
                 archive: BoundedArchive,
                 mutation: Mutation,
                 crossover: Crossover,
                 selection: Selection = BinaryTournamentSelection(
                     MultiComparator([FastNonDominatedRanking.get_comparator(),
                                      CrowdingDistance.get_comparator()])),
                 termination_criterion: TerminationCriterion = store.default_termination_criteria,
                 population_generator: Generator = store.default_generator,
                 population_evaluator: Evaluator = store.default_evaluator,
                 dominance_comparator: Comparator = store.default_comparator):
        """
        MOCEll implementation as described in:

        :param problem: The problem to solve.
        :param population_size: Size of the population.
        :param mutation: Mutation operator (see :py:mod:`jmetal.operator.mutation`).
        :param crossover: Crossover operator (see :py:mod:`jmetal.operator.crossover`).
        :param selection: Selection operator (see :py:mod:`jmetal.operator.selection`).
        """
        super(MOCell, self).__init__(
            problem=problem,
            population_size=population_size,
            offspring_population_size=1,
            mutation=mutation,
            crossover=crossover,
            selection=selection,
            termination_criterion=termination_criterion,
            population_evaluator=population_evaluator,
            population_generator=population_generator
        )
        self.dominance_comparator = dominance_comparator
        self.neighborhood = neighborhood
        self.archive = archive
        self.current_individual = 0
        self.current_neighbors = []

        self.comparator = MultiComparator([FastNonDominatedRanking.get_comparator(),
                                           CrowdingDistance.get_comparator()])

[docs]    def init_progress(self) -> None:
        super().init_progress()
        for solution in self.solutions:
            self.archive.add(copy.copy(solution))

[docs]    def update_progress(self) -> None:
        super().update_progress()
        self.current_individual = (self.current_individual + 1) % self.population_size

[docs]    def selection(self, population: List[S]):
        parents = []

        self.current_neighbors = self.neighborhood.get_neighbors(self.current_individual, population)
        self.current_neighbors.append(self.solutions[self.current_individual])

        parents.append(self.selection_operator.execute(self.current_neighbors))
        if len(self.archive.solution_list) > 0:
            parents.append(self.selection_operator.execute(self.archive.solution_list))
        else:
            parents.append(self.selection_operator.execute(self.current_neighbors))

        return parents

[docs]    def reproduction(self, mating_population: List[S]) -> List[S]:
        number_of_parents_to_combine = self.crossover_operator.get_number_of_parents()

        if len(mating_population) % number_of_parents_to_combine != 0:
            raise Exception('Wrong number of parents')

        offspring_population = self.crossover_operator.execute(mating_population)
        self.mutation_operator.execute(offspring_population[0])

        return [offspring_population[0]]

[docs]    def replacement(self, population: List[S], offspring_population: List[S]) -> List[List[S]]:
        result = self.dominance_comparator.compare(population[self.current_individual], offspring_population[0])

        if result == 1:  # the offspring individual dominates the current one
            population[self.current_individual] = offspring_population[0]
            self.archive.add(offspring_population[0])
        elif result == 0:  # the offspring and current individuals are non-dominated
            new_individual = offspring_population[0]

            self.current_neighbors.append(new_individual)

            ranking: Ranking = FastNonDominatedRanking()
            ranking.compute_ranking(self.current_neighbors)

            density_estimator: DensityEstimator = CrowdingDistance()
            for i in range(ranking.get_number_of_subfronts()):
                density_estimator.compute_density_estimator(ranking.get_subfront(i))

            self.current_neighbors.sort(key=cmp_to_key(self.comparator.compare))
            worst_solution = self.current_neighbors[-1]

            self.archive.add(new_individual)
            if worst_solution != new_individual:
                population[self.current_individual] = new_individual

        return population

[docs]    def get_result(self) -> R:
        return self.archive.solution_list

[docs]    def get_name(self) -> str:
        return 'MOCell'
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Source code for jmetal.algorithm.multiobjective.mocell
