001 /*
002 * Java Genetic Algorithm Library (jenetics-3.0.0).
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.Equality;
027 import org.jenetics.internal.util.Hash;
028
029 import org.jenetics.util.ISeq;
030 import org.jenetics.util.MSeq;
031 import org.jenetics.util.Mean;
032 import org.jenetics.util.RandomRegistry;
033 import org.jenetics.util.Seq;
034
035 /**
036 * <p>
037 * The order ({@link #getOrder()}) of this Recombination implementation is two.
038 * </p>
039 *
040 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
041 * @since 1.0
042 * @version 3.0 — <em>$Date: 2014-12-28 $</em>
043 */
044 public final class MeanAlterer<
045 G extends Gene<?, G> & Mean<G>,
046 C extends Comparable<? super C>
047 >
048 extends Recombinator<G, C>
049 {
050
051 /**
052 * Constructs an alterer with a given recombination probability.
053 *
054 * @param probability the crossover probability.
055 * @throws IllegalArgumentException if the {@code probability} is not in the
056 * valid range of {@code [0, 1]}.
057 */
058 public MeanAlterer(final double probability) {
059 super(probability, 2);
060 }
061
062 /**
063 * Create a new alterer with alter probability of {@code 0.05}.
064 */
065 public MeanAlterer() {
066 this(0.05);
067 }
068
069 @Override
070 protected int recombine(
071 final Population<G, C> population,
072 final int[] individuals,
073 final long generation
074 ) {
075 final Random random = RandomRegistry.getRandom();
076
077 final Phenotype<G, C> pt1 = population.get(individuals[0]);
078 final Phenotype<G, C> pt2 = population.get(individuals[1]);
079 final Genotype<G> gt1 = pt1.getGenotype();
080 final Genotype<G> gt2 = pt2.getGenotype();
081
082 final int cindex = random.nextInt(gt1.length());
083 final MSeq<Chromosome<G>> c1 = gt1.toSeq().copy();
084 final ISeq<Chromosome<G>> c2 = gt2.toSeq();
085
086 // Calculate the mean value of the gene array.
087 final MSeq<G> mean = mean(
088 c1.get(cindex).toSeq().copy(),
089 c2.get(cindex).toSeq()
090 );
091
092 c1.set(cindex, c1.get(cindex).newInstance(mean.toISeq()));
093
094 population.set(
095 individuals[0],
096 pt1.newInstance(gt1.newInstance(c1.toISeq()), generation)
097 );
098
099 return 1;
100 }
101
102 private static <G extends Gene<?, G> & Mean<G>>
103 MSeq<G> mean(final MSeq<G> a, final Seq<G> b) {
104 for (int i = a.length(); --i >= 0;) {
105 a.set(i, a.get(i).mean(b.get(i)));
106 }
107 return a;
108 }
109
110 @Override
111 public int hashCode() {
112 return Hash.of(getClass()).and(super.hashCode()).value();
113 }
114
115 @Override
116 public boolean equals(final Object obj) {
117 return Equality.of(this, obj).test(super::equals);
118 }
119
120 @Override
121 public String toString() {
122 return format("%s[p=%f]", getClass().getSimpleName(), _probability);
123 }
124
125 }
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