001 /*
002 * Java Genetic Algorithm Library (jenetics-1.5.0).
003 * Copyright (c) 2007-2013 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 import static org.jenetics.util.object.hashCodeOf;
024
025 import java.util.Random;
026
027 import javolution.lang.Immutable;
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 1.0 — <em>$Date: 2013-12-08 $</em>
043 */
044 public final class MeanAlterer<G extends Gene<?, G> & Mean<G>>
045 extends Recombinator<G>
046 implements Immutable
047 {
048
049 /**
050 * Constructs an alterer with a given recombination probability.
051 *
052 * @param probability the crossover probability.
053 * @throws IllegalArgumentException if the {@code probability} is not in the
054 * valid range of {@code [0, 1]}.
055 */
056 public MeanAlterer(final double probability) {
057 super(probability, 2);
058 }
059
060 /**
061 * Create a new alterer with alter probability of {@code 0.05}.
062 */
063 public MeanAlterer() {
064 this(0.05);
065 }
066
067 @Override
068 protected <C extends Comparable<? super C>> int recombine(
069 final Population<G, C> population,
070 final int[] individuals,
071 final int generation
072 ) {
073 final Random random = RandomRegistry.getRandom();
074
075 final Phenotype<G, C> pt1 = population.get(individuals[0]);
076 final Phenotype<G, C> pt2 = population.get(individuals[1]);
077 final Genotype<G> gt1 = pt1.getGenotype();
078 final Genotype<G> gt2 = pt2.getGenotype();
079
080 final int cindex = random.nextInt(gt1.length());
081 final MSeq<Chromosome<G>> c1 = gt1.toSeq().copy();
082 final ISeq<Chromosome<G>> c2 = gt2.toSeq();
083
084 // Calculate the mean value of the gene array.
085 final MSeq<G> mean = mean(
086 c1.get(cindex).toSeq().copy(),
087 c2.get(cindex).toSeq()
088 );
089
090 c1.set(cindex, c1.get(cindex).newInstance(mean.toISeq()));
091
092 population.set(
093 individuals[0],
094 pt1.newInstance(gt1.newInstance(c1.toISeq()), generation)
095 );
096
097 return 1;
098 }
099
100 private static <G extends Gene<?, G> & Mean<G>>
101 MSeq<G> mean(final MSeq<G> a, final Seq<G> b) {
102 for (int i = a.length(); --i >= 0;) {
103 a.set(i, a.get(i).mean(b.get(i)));
104 }
105 return a;
106 }
107
108 @Override
109 public int hashCode() {
110 return hashCodeOf(getClass()).and(super.hashCode()).value();
111 }
112
113 @Override
114 public boolean equals(final Object obj) {
115 return obj == this || obj instanceof MeanAlterer<?> && super.equals(obj);
116 }
117
118 @Override
119 public String toString() {
120 return format("%s[p=%f]", getClass().getSimpleName(), _probability);
121 }
122
123 }
124
|