RandomKeyMutation.java :  » Science » Apache-commons-math-2.0 » org » apache » commons » math » genetics » Java Open Source

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Apache commons math 2.0 » org » apache » commons » math » genetics » RandomKeyMutation.java
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.math.genetics;

import java.util.ArrayList;
import java.util.List;

import org.apache.commons.math.MathRuntimeException;

/**
 * Mutation operator for {@link RandomKey}s. Changes a randomly chosen element
 * of the array representation to a random value uniformly distributed in [0,1].
 * 
 * @since 2.0
 * @version $Revision: 799857 $ $Date: 2009-08-01 09:07:12 -0400 (Sat, 01 Aug 2009) $
 */
public class RandomKeyMutation implements MutationPolicy {

    /**
     * {@inheritDoc}
     * 
     * @throws IllegalArgumentException if <code>original</code> is not a 
     * {@link RandomKey} instance
     */
    public Chromosome mutate(Chromosome original) {
        if (!(original instanceof RandomKey<?>)) {
            throw MathRuntimeException.createIllegalArgumentException(
                    "RandomKeyMutation works only with RandomKeys, got " +
                    original.getClass().getSimpleName());
        }
        
        RandomKey<?> originalRk = (RandomKey<?>) original;
        List<Double> repr = originalRk.getRepresentation();
        int rInd = GeneticAlgorithm.getRandomGenerator().nextInt(repr.size());
        
        List<Double> newRepr = new ArrayList<Double> (repr);
        newRepr.set(rInd, GeneticAlgorithm.getRandomGenerator().nextDouble());
        
        return originalRk.newFixedLengthChromosome(newRepr);
    }

}
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