001 /*
002 * CISELab, Computational and Intelligent Systems Engineering Laboratory
003 * Department of Engineering
004 * University of Sannio, 82100 Benevento (ITALY)
005 * web-site: www.ciselab.org
006 *
007 * JENES, A Java Library for Genetic Algorithms
008 * Copyright (C) 2009, Luigi Troiano
009 *
010 * This library is free software; you can redistribute it and/or
011 * modify it under the terms of the GNU Lesser General Public
012 * License as published by the Free Software Foundation; either
013 * version 2.1 of the License, or (at your option) any later version.
014 *
015 * This library is distributed in the hope that it will be useful,
016 * but WITHOUT ANY WARRANTY; without even the implied warranty of
017 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
018 * Lesser General Public License for more details.
019 *
020 * You should have received a copy of the GNU Lesser General Public
021 * License along with this library; if not, write to the Free Software
022 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
023 02110-1301 USA
024 *
025 * COPYRIGHT DISCLAIMER
026 * CISELab, hereby disclaims all copyright interest in the
027 * library `JENES' (A Java Library for Genetic Algorithms)
028 * written by Luigi Troiano et al.
029 *
030 * Luigi Troiano, 1 January 2009
031 * CISELab Coordinator
032 */
033 package jenes.tutorials.problem3;
034
035 import jenes.Random;
036 import jenes.chromosome.Chromosome;
037 import jenes.chromosome.IntegerChromosome;
038 import jenes.population.Individual;
039 import jenes.stage.operator.Mutator;
040
041 /**Algorithm description:
042 * Two random indexes, i1 and i2, are choosed; the order of the elements within the
043 * range [i1,i2] changes randomly.
044 *
045 * e.g.
046 * i1=0; i2=3
047 * position: 0 1 2 3 4 5
048 * start_chrom: 5 2 1 4 6 3
049 * end_chrom: 2 5 4 1 6 3
050 */
051 public class TSPScrambleMutator<T extends Chromosome> extends Mutator<T> {
052
053 public TSPScrambleMutator(double pMut) {
054 super(pMut);
055 }
056
057 @Override
058 protected void mutate(Individual<T> t) {
059 int size = t.getChromosomeLength();
060 int index1,index2;
061 do{
062 index1 = Random.getInstance().nextInt(0,size);
063 index2 = Random.getInstance().nextInt(0,size);
064 }while(index2==index1);
065
066 int min,max;
067 if(index1<index2){
068 min=index1;
069 max=index2;
070 }else{
071 min=index2;
072 max=index1;
073 }
074
075 randomize(t,min, max);
076 }
077
078 /**
079 * Randomizes the elements chromosome within the range [min,max]
080 * <p>
081 * @param c the individual to mutate
082 * @param min the lower bound
083 * @param max the upper bound
084 */
085 public void randomize(Individual<T> c,int min, int max) {
086 IntegerChromosome chrom = (IntegerChromosome) c.getChromosome();
087 //we create a temporany array
088 int len = max-min+1;
089 int[] base = new int[len];
090 //we fill it with the elements within [min,max]
091 for(int i=0;i<len;i++)
092 base[i]= chrom.getValue(min+i);
093
094 //a randomizes process starts
095 int i=0;
096 //the loop ends when the temporany array is empty
097 while(len!=0){
098 //we choose a random position pos in the array and copy the element at pos in the chromosome
099 int pos = Random.getInstance().nextInt(0,len);
100 chrom.setValue(min+i,base[pos]);
101 //we removes the choosed element from the temporany array
102 for(int j=pos;j<(len-1);j++){
103 base[j]=base[j+1];
104 }
105 //we updates len and i
106 len--;i++;
107 }
108 }
109 }
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