001 /*
002 * Java Genetic Algorithm Library (jenetics-2.0.2).
003 * Copyright (c) 2007-2014 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@gmx.at)
019 */
020 package org.jenetics;
021
022 import static java.lang.String.format;
023
024 import java.util.Random;
025
026 import org.jenetics.internal.util.HashBuilder;
027
028 import org.jenetics.util.ISeq;
029 import org.jenetics.util.MSeq;
030 import org.jenetics.util.Mean;
031 import org.jenetics.util.RandomRegistry;
032 import org.jenetics.util.Seq;
033
034 /**
035 * <p>
036 * The order ({@link #getOrder()}) of this Recombination implementation is two.
037 * </p>
038 *
039 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
040 * @since 1.0
041 * @version 2.0 — <em>$Date: 2014-03-12 $</em>
042 */
043 public final class MeanAlterer<G extends Gene<?, G> & Mean<G>>
044 extends Recombinator<G>
045 {
046
047 /**
048 * Constructs an alterer with a given recombination probability.
049 *
050 * @param probability the crossover probability.
051 * @throws IllegalArgumentException if the {@code probability} is not in the
052 * valid range of {@code [0, 1]}.
053 */
054 public MeanAlterer(final double probability) {
055 super(probability, 2);
056 }
057
058 /**
059 * Create a new alterer with alter probability of {@code 0.05}.
060 */
061 public MeanAlterer() {
062 this(0.05);
063 }
064
065 @Override
066 protected <C extends Comparable<? super C>> int recombine(
067 final Population<G, C> population,
068 final int[] individuals,
069 final int generation
070 ) {
071 final Random random = RandomRegistry.getRandom();
072
073 final Phenotype<G, C> pt1 = population.get(individuals[0]);
074 final Phenotype<G, C> pt2 = population.get(individuals[1]);
075 final Genotype<G> gt1 = pt1.getGenotype();
076 final Genotype<G> gt2 = pt2.getGenotype();
077
078 final int cindex = random.nextInt(gt1.length());
079 final MSeq<Chromosome<G>> c1 = gt1.toSeq().copy();
080 final ISeq<Chromosome<G>> c2 = gt2.toSeq();
081
082 // Calculate the mean value of the gene array.
083 final MSeq<G> mean = mean(
084 c1.get(cindex).toSeq().copy(),
085 c2.get(cindex).toSeq()
086 );
087
088 c1.set(cindex, c1.get(cindex).newInstance(mean.toISeq()));
089
090 population.set(
091 individuals[0],
092 pt1.newInstance(gt1.newInstance(c1.toISeq()), generation)
093 );
094
095 return 1;
096 }
097
098 private static <G extends Gene<?, G> & Mean<G>>
099 MSeq<G> mean(final MSeq<G> a, final Seq<G> b) {
100 for (int i = a.length(); --i >= 0;) {
101 a.set(i, a.get(i).mean(b.get(i)));
102 }
103 return a;
104 }
105
106 @Override
107 public int hashCode() {
108 return HashBuilder.of(getClass()).and(super.hashCode()).value();
109 }
110
111 @Override
112 public boolean equals(final Object obj) {
113 return obj == this || obj instanceof MeanAlterer<?> && super.equals(obj);
114 }
115
116 @Override
117 public String toString() {
118 return format("%s[p=%f]", getClass().getSimpleName(), _probability);
119 }
120
121 }
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