RandomKeyMutation.java revision dee0849a9704d532af0b550146cbafbaa6ee1d19 
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 */
17package org.apache.commons.math.genetics;
18
19import java.util.ArrayList;
20import java.util.List;
21
22import org.apache.commons.math.MathRuntimeException;
23import org.apache.commons.math.exception.util.LocalizedFormats;
24
25/**
26 * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
27 * of the array representation to a random value uniformly distributed in [0,1].
28 *
29 * @since 2.0
30 * @version $Revision: 983921 $ $Date: 2010-08-10 12:46:06 +0200 (mar. 10 août 2010) $
31 */
32public class RandomKeyMutation implements MutationPolicy {
33
34    /**
35     * {@inheritDoc}
36     *
37     * @throws IllegalArgumentException if <code>original</code> is not a
38     * {@link RandomKey} instance
39     */
40    public Chromosome mutate(Chromosome original) {
41        if (!(original instanceof RandomKey<?>)) {
42            throw MathRuntimeException.createIllegalArgumentException(
43                    LocalizedFormats.RANDOMKEY_MUTATION_WRONG_CLASS,
44                    original.getClass().getSimpleName());
45        }
46
47        RandomKey<?> originalRk = (RandomKey<?>) original;
48        List<Double> repr = originalRk.getRepresentation();
49        int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
50
51        List<Double> newRepr = new ArrayList<Double> (repr);
52        newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
53
54        return originalRk.newFixedLengthChromosome(newRepr);
55    }
56
57}
58