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.math.genetics;
18
19 import java.util.ArrayList;
20 import java.util.List;
21
22 import org.apache.commons.math.MathRuntimeException;
23
24 /**
25 * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
26 * of the array representation to a random value uniformly distributed in [0,1].
27 *
28 * @since 2.0
29 * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
30 */
31 public class RandomKeyMutation implements MutationPolicy {
32
33 /**
34 * {@inheritDoc}
35 *
36 * @throws IllegalArgumentException if <code>original</code> is not a
37 * {@link RandomKey} instance
38 */
39 public Chromosome mutate(Chromosome original) {
40 if (!(original instanceof RandomKey<?>)) {
41 throw MathRuntimeException.createIllegalArgumentException(
42 "RandomKeyMutation works only with RandomKeys, got " +
43 original.getClass().getSimpleName());
44 }
45
46 RandomKey<?> originalRk = (RandomKey<?>) original;
47 List<Double> repr = originalRk.getRepresentation();
48 int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
49
50 List<Double> newRepr = new ArrayList<Double> (repr);
51 newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
52
53 return originalRk.newFixedLengthChromosome(newRepr);
54 }
55
56 }