1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.math4.legacy.genetics;
18
19 import java.util.ArrayList;
20 import java.util.List;
21
22 import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
23 import org.apache.commons.math4.legacy.exception.util.LocalizedFormats;
24
25 /**
26 * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
27 *
28 * @since 2.0
29 */
30 public class BinaryMutation implements MutationPolicy {
31
32 /**
33 * Mutate the given chromosome. Randomly changes one gene.
34 *
35 * @param original the original chromosome.
36 * @return the mutated chromosome.
37 * @throws MathIllegalArgumentException if <code>original</code> is not an instance of {@link BinaryChromosome}.
38 */
39 @Override
40 public Chromosome mutate(Chromosome original) throws MathIllegalArgumentException {
41 if (!(original instanceof BinaryChromosome)) {
42 throw new MathIllegalArgumentException(LocalizedFormats.INVALID_BINARY_CHROMOSOME);
43 }
44
45 BinaryChromosome origChrom = (BinaryChromosome) original;
46 List<Integer> newRepr = new ArrayList<>(origChrom.getRepresentation());
47
48 // randomly select a gene
49 int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
50 // and change it
51 newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);
52
53 return origChrom.newFixedLengthChromosome(newRepr);
54 }
55 }