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.math3.genetics;
018
019 import java.util.ArrayList;
020 import java.util.List;
021
022 import org.apache.commons.math3.exception.MathIllegalArgumentException;
023 import org.apache.commons.math3.exception.util.LocalizedFormats;
024
025 /**
026 * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
027 *
028 * @version $Id: BinaryMutation.java 1416643 2012-12-03 19:37:14Z tn $
029 * @since 2.0
030 */
031 public class BinaryMutation implements MutationPolicy {
032
033 /**
034 * Mutate the given chromosome. Randomly changes one gene.
035 *
036 * @param original the original chromosome.
037 * @return the mutated chromosome.
038 * @throws MathIllegalArgumentException if <code>original</code> is not an instance of {@link BinaryChromosome}.
039 */
040 public Chromosome mutate(Chromosome original) throws MathIllegalArgumentException {
041 if (!(original instanceof BinaryChromosome)) {
042 throw new MathIllegalArgumentException(LocalizedFormats.INVALID_BINARY_CHROMOSOME);
043 }
044
045 BinaryChromosome origChrom = (BinaryChromosome) original;
046 List<Integer> newRepr = new ArrayList<Integer>(origChrom.getRepresentation());
047
048 // randomly select a gene
049 int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
050 // and change it
051 newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
052
053 Chromosome newChrom = origChrom.newFixedLengthChromosome(newRepr);
054 return newChrom;
055 }
056
057 }