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
025 import io.jenetics.internal.util.Requires;
026 import io.jenetics.util.MSeq;
027 import io.jenetics.util.RandomRegistry;
028
029 /**
030 * This alterer takes two chromosomes (treating it as vectors) and creates a
031 * linear combination of these vectors as a result. The line-recombination depends
032 * on a variable <em>p</em> which determines how far out along the line (defined
033 * by the two multidimensional points/vectors) the children are allowed to be.
034 * If <em>p</em> = 0 then the children will be located along the line within the
035 * hypercube between the two points. If <em>p</em> > 0 then the children may
036 * be located anywhere on the line, even somewhat outside the hypercube.
037 * <p>
038 * Points outside the allowed numeric range are rejected, and new points are
039 * generated until they lie in the valid range. The strategy on how
040 * out-of-range points are handled, is the difference to the very similar
041 * {@link LineCrossover}.
042 *
043 * @see <a href="https://cs.gmu.edu/~sean/book/metaheuristics/"><em>
044 * Essentials of Metaheuristic, page 42</em></a>
045 * @see LineCrossover
046 *
047 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
048 * @version 3.8
049 * @since 3.8
050 */
051 public class IntermediateCrossover<
052 G extends NumericGene<?, G>,
053 C extends Comparable<? super C>
054 >
055 extends Crossover<G, C>
056 {
057
058 private final double _p;
059
060 /**
061 * Creates a new intermediate-crossover with the given recombination
062 * probability and the line-scaling factor <em>p</em>.
063 * <p>
064 * <b>When the value for <em>p</em> is greater then 0, the crossover point
065 * generation must be repeated until the points lie within the allowed
066 * range. Values greater then 10 are usually not recommended, since this
067 * leads to unnecessary crossover point generation.</b>
068 *
069 * @param probability the recombination probability.
070 * @param p defines the possible location of the recombined chromosomes. If
071 * <em>p</em> = 0 then the children will be located along the line
072 * within the hypercube between the two points. If <em>p</em> > 0
073 * then the children may be located anywhere on the line, even
074 * somewhat outside the hypercube.
075 * @throws IllegalArgumentException if the {@code probability} is not in the
076 * valid range of {@code [0, 1]} or if {@code p} is smaller then zero
077 */
078 public IntermediateCrossover(final double probability, final double p) {
079 super(probability);
080 _p = Requires.nonNegative(p, "p");
081 }
082
083 /**
084 * Creates a new intermediate-crossover with the given recombination
085 * probability. The parameter <em>p</em> is set to zero, which restricts the
086 * recombined chromosomes within the hypercube of the selected chromosomes
087 * (vectors).
088 *
089 * @param probability the recombination probability.
090 * @throws IllegalArgumentException if the {@code probability} is not in the
091 * valid range of {@code [0, 1]}
092 */
093 public IntermediateCrossover(final double probability) {
094 this(probability, 0);
095 }
096
097 /**
098 * Creates a new intermediate-crossover with default recombination
099 * probability ({@link #DEFAULT_ALTER_PROBABILITY}) and a <em>p</em> value
100 * of zero, which restricts the recombined chromosomes within the hypercube
101 * of the selected chromosomes (vectors).
102 */
103 public IntermediateCrossover() {
104 this(DEFAULT_ALTER_PROBABILITY, 0);
105 }
106
107 @Override
108 protected int crossover(final MSeq<G> v, final MSeq<G> w) {
109 final var random = RandomRegistry.random();
110
111 final double min = v.get(0).min().doubleValue();
112 final double max = v.get(0).max().doubleValue();
113
114 for (int i = 0, n = min(v.length(), w.length()); i < n; ++i) {
115 final var g1 = v.get(i);
116 final var g2 = w.get(i);
117
118 if (g1.isValid() && g2.isValid()) {
119 final double vi = g1.doubleValue();
120 final double wi = g2.doubleValue();
121
122 double t, s;
123 do {
124 final double a = random.nextDouble(-_p, 1 + _p);
125 final double b = random.nextDouble(-_p, 1 + _p);
126
127 t = a*vi + (1 - a)*wi;
128 s = b*wi + (1 - b)*vi;
129 } while (t < min || s < min || t >= max || s >= max);
130
131 v.set(i, v.get(i).newInstance(t));
132 w.set(i, w.get(i).newInstance(s));
133 }
134 }
135
136 return 2;
137 }
138
139 @Override
140 public String toString() {
141 return format("%s[p=%f]", getClass().getSimpleName(), _probability);
142 }
143
144 }
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