com.ciphertool.genetics.algorithms.selection.modes.TournamentSelector.java Source code

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Here is the source code for com.ciphertool.genetics.algorithms.selection.modes.TournamentSelector.java

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/**
 * Copyright 2012 George Belden
 * 
 * This file is part of ZodiacGenetics.
 * 
 * ZodiacGenetics is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, either version 3 of the License, or (at your option) any
 * later version.
 * 
 * ZodiacGenetics is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU General Public License along with
 * ZodiacGenetics. If not, see <http://www.gnu.org/licenses/>.
 */
package com.ciphertool.genetics.algorithms.selection.modes;

import java.util.Collections;
import java.util.List;

import org.springframework.beans.factory.annotation.Required;

import com.ciphertool.genetics.entities.Chromosome;
import com.ciphertool.genetics.util.DescendingFitnessComparator;
import com.ciphertool.genetics.util.FitnessComparator;

public class TournamentSelector implements Selector {
    private Double selectionAccuracy;
    private static FitnessComparator fitnessComparator = new DescendingFitnessComparator();

    @Override
    public int getNextIndex(List<Chromosome> individuals, Double totalFitness) {
        Collections.sort(individuals, fitnessComparator);

        for (int i = 0; i < individuals.size(); i++) {
            if (Math.random() <= selectionAccuracy) {
                return i;
            }
        }

        // return the least fit individual since it won the tournament
        return individuals.size() - 1;
    }

    /**
     * @param selectionAccuracy
     *            the selectionAccuracy to set
     */
    @Required
    public void setSelectionAccuracy(Double selectionAccuracy) {
        if (selectionAccuracy < 0.0 || selectionAccuracy > 1.0) {
            throw new IllegalArgumentException("Tried to set a selectionAccuracy of " + selectionAccuracy
                    + ", but TournamentSelector requires a selectionAccuracy between 0.0 and 1.0 inclusive.");
        }

        this.selectionAccuracy = selectionAccuracy;
    }
}