/*
* RapidMiner
*
* Copyright (C) 2001-2008 by Rapid-I and the contributors
*
* Complete list of developers available at our web site:
*
* http://rapid-i.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.operator.features.weighting;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Random;
import com.rapidminer.example.Attribute;
import com.rapidminer.example.set.AttributeWeightedExampleSet;
import com.rapidminer.operator.features.Individual;
import com.rapidminer.operator.features.Population;
import com.rapidminer.operator.features.PopulationOperator;
import com.rapidminer.operator.features.selection.SelectionCrossover;
/**
* Crossover operator for the used weights of example sets. An example set is
* selected with a given fixed propability and a mating partner is determined
* randomly. Crossover can be either one point, uniform, or shuffle. Only useful
* if all example sets have the same attributes and do not contain value series.
*
* @author Ingo Mierswa
* @version $Id: WeightingCrossover.java,v 1.15 2006/04/14 07:47:17 ingomierswa
* Exp $
*/
public class WeightingCrossover implements PopulationOperator {
private int type;
private double prob;
private Random random;
public WeightingCrossover(int type, double prob, Random random) {
this.prob = prob;
this.type = type;
this.random = random;
}
/** The default implementation returns true for every generation. */
public boolean performOperation(int generation) {
return true;
}
public void crossover(AttributeWeightedExampleSet es1, AttributeWeightedExampleSet es2) {
switch (type) {
case SelectionCrossover.ONE_POINT:
int n = 1 + random.nextInt(es1.getAttributes().size() - 1);
int counter = 0;
for (Attribute attribute : es1.getAttributes()) {
if (counter >= n) {
double dummy = es1.getWeight(attribute);
es1.setWeight(attribute, es2.getWeight(attribute));
es2.setWeight(attribute, dummy);
}
counter++;
}
break;
case SelectionCrossover.UNIFORM:
boolean[] swap = new boolean[es1.getAttributes().size()];
for (int i = 0; i < swap.length; i++) {
swap[i] = random.nextBoolean();
}
swapWeights(es1, es2, swap);
break;
case SelectionCrossover.SHUFFLE:
swap = new boolean[es1.getAttributes().size()];
List<Integer> indices = new ArrayList<Integer>();
for (int i = 0; i < swap.length; i++) {
indices.add(i);
}
if (indices.size() > 0) {
int toSwap = random.nextInt(indices.size() - 1) + 1;
for (int i = 0; i < toSwap; i++) {
swap[indices.remove(random.nextInt(indices.size()))] = true;
}
}
swapWeights(es1, es2, swap);
break;
default:
break;
}
}
private void swapWeights(AttributeWeightedExampleSet es1, AttributeWeightedExampleSet es2, boolean[] swap) {
int index = 0;
for (Attribute attribute : es1.getAttributes()) {
if (swap[index++]) {
double dummy = es1.getWeight(attribute);
es1.setWeight(attribute, es2.getWeight(attribute));
es2.setWeight(attribute, dummy);
}
}
}
public void operate(Population population) {
if (population.getNumberOfIndividuals() < 2)
return;
LinkedList<AttributeWeightedExampleSet> matingPool = new LinkedList<AttributeWeightedExampleSet>();
for (int i = 0; i < population.getNumberOfIndividuals(); i++)
matingPool.add((AttributeWeightedExampleSet) population.get(i).getExampleSet().clone());
List<Individual> l = new LinkedList<Individual>();
while (matingPool.size() > 1) {
AttributeWeightedExampleSet p1 = matingPool.remove(random.nextInt(matingPool.size()));
AttributeWeightedExampleSet p2 = matingPool.remove(random.nextInt(matingPool.size()));
if (random.nextDouble() < prob) {
crossover(p1, p2);
if (p1.getNumberOfUsedAttributes() > 0)
l.add(new Individual(p1));
if (p2.getNumberOfUsedAttributes() > 0)
l.add(new Individual(p2));
}
}
population.addAllIndividuals(l);
}
}