001 /*
002 * Java Genetic Algorithm Library (jenetics-8.0.0).
003 * Copyright (c) 2007-2024 Franz Wilhelmstötter
004 *
005 * Licensed under the Apache License, Version 2.0 (the "License");
006 * you may not use this file except in compliance with the License.
007 * 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 * Author:
018 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
019 */
020 package io.jenetics;
021
022 import static java.lang.Math.min;
023 import static java.lang.String.format;
024 import static java.util.Objects.requireNonNull;
025
026 import java.util.function.BinaryOperator;
027
028 import io.jenetics.util.BaseSeq;
029 import io.jenetics.util.MSeq;
030 import io.jenetics.util.RandomRegistry;
031
032 /**
033 * Alters a chromosome by replacing two genes by the result of a given
034 * <em>combiner</em> function.
035 *
036 * <p>
037 * The order ({@link #order()}) of this recombination implementation is two.
038 * </p>
039 *
040 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
041 * @since 6.0
042 * @version 6.0
043 */
044 public class CombineAlterer<
045 G extends Gene<?, G>,
046 C extends Comparable<? super C>
047 >
048 extends Recombinator<G, C>
049 {
050
051 private final BinaryOperator<G> _combiner;
052
053 /**
054 * Create a new combiner alterer with the given arguments.
055 *
056 * @param combiner the function used for combining two genes
057 * @param probability The recombination probability.
058 * @throws IllegalArgumentException if the {@code probability} is not in the
059 * valid range of {@code [0, 1]}
060 * @throws NullPointerException if the given {@code combiner} is {@code null}
061 */
062 public CombineAlterer(
063 final BinaryOperator<G> combiner,
064 final double probability
065 ) {
066 super(probability, 2);
067 _combiner = requireNonNull(combiner);
068 }
069
070 /**
071 * Create a new combiner alterer with the given arguments.
072 *
073 * @param combiner the function used for combining two genes
074 * @throws IllegalArgumentException if the {@code probability} is not in the
075 * valid range of {@code [0, 1]}
076 * @throws NullPointerException if the given {@code combiner} is {@code null}
077 */
078 public CombineAlterer(final BinaryOperator<G> combiner) {
079 this(combiner, DEFAULT_ALTER_PROBABILITY);
080 }
081
082 /**
083 * Return the combiner function, used by {@code this} alterer.
084 *
085 * @return the combiner function, used by {@code this} alterer
086 */
087 public BinaryOperator<G> combiner() {
088 return _combiner;
089 }
090
091 @Override
092 protected int recombine(
093 final MSeq<Phenotype<G, C>> population,
094 final int[] individuals,
095 final long generation
096 ) {
097 final Phenotype<G, C> pt1 = population.get(individuals[0]);
098 final Phenotype<G, C> pt2 = population.get(individuals[1]);
099 final Genotype<G> gt1 = pt1.genotype();
100 final Genotype<G> gt2 = pt2.genotype();
101
102 //Choosing the Chromosome index for crossover.
103 final int ci = RandomRegistry.random()
104 .nextInt(min(gt1.length(), gt2.length()));
105
106 final MSeq<Chromosome<G>> c1 = MSeq.of(gt1);
107
108 // Calculate the mean value of the gene array.
109 final MSeq<G> mean = combine(c1.get(ci), gt2.get(ci), _combiner);
110
111 c1.set(ci, c1.get(ci).newInstance(mean.toISeq()));
112 population.set(individuals[0], Phenotype.of(Genotype.of(c1), generation));
113
114 return 1;
115 }
116
117 private static <G extends Gene<?, G>>
118 MSeq<G> combine(
119 final BaseSeq<G> a,
120 final BaseSeq<G> b,
121 final BinaryOperator<G> combiner
122 ) {
123 final MSeq<G> result = MSeq.ofLength(a.length());
124 for (int i = a.length(); --i >= 0;) {
125 result.set(i, combiner.apply(a.get(i), b.get(i)));
126 }
127 return result;
128 }
129
130 @Override
131 public String toString() {
132 return format("%s[p=%f]", getClass().getSimpleName(), _probability);
133 }
134 }
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