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 }