BinaryMutation.java

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

  20. import org.apache.commons.math4.legacy.exception.MathIllegalArgumentException;
  21. import org.apache.commons.math4.legacy.exception.util.LocalizedFormats;

  22. /**
  23.  * Mutation for {@link BinaryChromosome}s. Randomly changes one gene.
  24.  *
  25.  * @since 2.0
  26.  */
  27. public class BinaryMutation implements MutationPolicy {

  28.     /**
  29.      * Mutate the given chromosome. Randomly changes one gene.
  30.      *
  31.      * @param original the original chromosome.
  32.      * @return the mutated chromosome.
  33.      * @throws MathIllegalArgumentException if <code>original</code> is not an instance of {@link BinaryChromosome}.
  34.      */
  35.     @Override
  36.     public Chromosome mutate(Chromosome original) throws MathIllegalArgumentException {
  37.         if (!(original instanceof BinaryChromosome)) {
  38.             throw new MathIllegalArgumentException(LocalizedFormats.INVALID_BINARY_CHROMOSOME);
  39.         }

  40.         BinaryChromosome origChrom = (BinaryChromosome) original;
  41.         List<Integer> newRepr = new ArrayList<>(origChrom.getRepresentation());

  42.         // randomly select a gene
  43.         int geneIndex = GeneticAlgorithm.getRandomGenerator().nextInt(origChrom.getLength());
  44.         // and change it
  45.         newRepr.set(geneIndex, origChrom.getRepresentation().get(geneIndex) == 0 ? 1 : 0);

  46.         return origChrom.newFixedLengthChromosome(newRepr);
  47.     }
  48. }