001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math.genetics;
018
019 import java.util.ArrayList;
020 import java.util.List;
021
022 /**
023 * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
024 *
025 * @version $Revision: 811685 $ $Date: 2009-09-05 19:36:48 +0200 (sam. 05 sept. 2009) $
026 * @since 2.0
027 */
028 public class BinaryMutation implements MutationPolicy {
029
030 /**
031 * Mutate the given chromosome. Randomly changes one gene.
032 * @param original the original chromosome.
033 * @return the mutated chromomsome.
034 */
035 public Chromosome mutate(Chromosome original) {
036 if (!(original instanceof BinaryChromosome)) {
037 throw new IllegalArgumentException("Binary mutation works on BinaryChromosome only.");
038 }
039
040 BinaryChromosome origChrom = (BinaryChromosome) original;
041 List<Integer> newRepr = new ArrayList<Integer>(origChrom.getRepresentation());
042
043 // randomly select a gene
044 int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
045 // and change it
046 newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
047
048 Chromosome newChrom = origChrom.newFixedLengthChromosome(newRepr);
049 return newChrom;
050 }
051
052 }