001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements. See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License. You may obtain a copy of the License at
008 *
009 * http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017 package org.apache.commons.math.genetics;
018
019 import java.util.ArrayList;
020 import java.util.List;
021
022 import org.apache.commons.math.MathRuntimeException;
023
024 /**
025 * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
026 * of the array representation to a random value uniformly distributed in [0,1].
027 *
028 * @since 2.0
029 * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $
030 */
031 public class RandomKeyMutation implements MutationPolicy {
032
033 /**
034 * {@inheritDoc}
035 *
036 * @throws IllegalArgumentException if <code>original</code> is not a
037 * {@link RandomKey} instance
038 */
039 public Chromosome mutate(Chromosome original) {
040 if (!(original instanceof RandomKey<?>)) {
041 throw MathRuntimeException.createIllegalArgumentException(
042 "RandomKeyMutation works only with RandomKeys, got " +
043 original.getClass().getSimpleName());
044 }
045
046 RandomKey<?> originalRk = (RandomKey<?>) original;
047 List<Double> repr = originalRk.getRepresentation();
048 int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
049
050 List<Double> newRepr = new ArrayList<Double> (repr);
051 newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
052
053 return originalRk.newFixedLengthChromosome(newRepr);
054 }
055
056 }