01 /*
02 * JENES
03 * A time and memory efficient Java library for genetic algorithms and more
04 * Copyright (C) 2011 Intelligentia srl
05 *
06 * This program is free software: you can redistribute it and/or modify
07 * it under the terms of the GNU General Public License as published by
08 * the Free Software Foundation, either version 3 of the License, or
09 * (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 */
19 package jenes.tutorials.problem4;
20
21 import jenes.Fitness;
22 import jenes.chromosome.DoubleChromosome;
23 import jenes.population.Individual;
24
25 /**
26 *
27 * @author Luigi Troiano
28 */
29 public class EntropyFitness extends Fitness<DoubleChromosome> {
30
31 public static EntropyFitness MAX = new EntropyFitness(true);
32 public static EntropyFitness MIN = new EntropyFitness(false);
33
34 private EntropyFitness(boolean maximize) {
35 super(maximize);
36 }
37
38 @Override
39 public void evaluate(Individual<DoubleChromosome> individual) {
40 DoubleChromosome chrom = individual.getChromosome();
41
42 int length = chrom.length();
43
44 double sum = 0.0;
45 for (int i = 0; i < length; ++i) {
46 sum += chrom.getValue(i);
47 }
48
49 double entropy = 0.0;
50 for (int i = 0; i < length; ++i) {
51 double pxi = chrom.getValue(i) / sum;
52 chrom.setValue(i, pxi);
53
54 entropy -= (pxi * Math.log(pxi) / Math.log(2));
55 }
56
57 individual.setScore(entropy);
58 }
59 }
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