/**
* Copyright (C) 2001-2017 by RapidMiner and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapidminer.com
*
* This program is free software: you can redistribute it and/or modify it under the terms of the
* GNU Affero General Public License as published by the Free Software Foundation, either version 3
* of the License, or (at your option) any later version.
*
* This program 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
* Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License along with this program.
* If not, see http://www.gnu.org/licenses/.
*/
package com.rapidminer.tools.math.optimization.ec.es;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;
/**
* Crossover operator for the values of an evolution strategies optimization. An individual is
* selected with a given fixed propability and a mating partner is determined randomly. This class
* only impplements uniform crossover.
*
* @author Ingo Mierswa
*/
public class Crossover implements PopulationOperator {
private double prob;
private Random random;
public Crossover(double prob, Random random) {
this.prob = prob;
this.random = random;
}
public void crossover(Individual i1, Individual i2) {
double[] values1 = i1.getValues();
double[] values2 = i2.getValues();
boolean[] swap = new boolean[values1.length];
for (int i = 0; i < swap.length; i++) {
swap[i] = random.nextBoolean();
}
for (int i = 0; i < swap.length; i++) {
if (swap[i]) {
double dummy = values1[i];
values1[i] = values2[i];
values2[i] = dummy;
}
}
i1.setValues(values1);
i2.setValues(values2);
}
@Override
public void operate(Population population) {
if (population.getNumberOfIndividuals() < 2) {
return;
}
List<Individual> matingPool = new LinkedList<Individual>();
for (int i = 0; i < population.getNumberOfIndividuals(); i++) {
matingPool.add((Individual) population.get(i).clone());
}
List<Individual> l = new LinkedList<Individual>();
while (matingPool.size() > 1) {
Individual p1 = matingPool.remove(random.nextInt(matingPool.size()));
Individual p2 = matingPool.remove(random.nextInt(matingPool.size()));
if (random.nextDouble() < prob) {
crossover(p1, p2);
l.add(p1);
l.add(p2);
}
}
population.addAll(l);
}
}