001 /*
002 * Java Genetic Algorithm Library (jenetics-7.1.1).
003 * Copyright (c) 2007-2022 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.ext;
021
022 import static java.lang.String.format;
023
024 import io.jenetics.util.ISeq;
025 import io.jenetics.util.RandomRegistry;
026
027 import io.jenetics.ext.util.TreeNode;
028
029 /**
030 * Swaps two, randomly chosen, nodes (sub-trees) from two given trees.
031 * <pre> {@code
032 * Tree A Tree B
033 * 0 a
034 * ├── 1 ├── b
035 * │ ├── 4 │ ├── e
036 * │ └── 5 │ └── f
037 * ├── 2 ├── c
038 * │ └── 6 │ └── g
039 * └── 3 └── d
040 * ├── 7 ├── h
041 * │ ├── 10 │ ├── k
042 * │ └── 11 │ └── l
043 * ├── 8 ├── i
044 * └── 9 └── j
045 *
046 * Swap node "3" of A with node "c" of B
047 *
048 * 0 a
049 * ├── 1 ├── b
050 * │ ├── 4 │ ├── e
051 * │ └── 5 │ └── f
052 * ├── 2 ├── 3
053 * │ └── 6 │ ├── 7
054 * └── c │ │ ├── 10
055 * └── g │ │ └── 11
056 * │ ├── 8
057 * │ └── 9
058 * └── d
059 * ├── h
060 * │ ├── k
061 * │ └── l
062 * ├── i
063 * └── j
064 * }</pre>
065 *
066 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
067 * @version 5.0
068 * @since 3.9
069 */
070 public class SingleNodeCrossover<
071 G extends TreeGene<?, G>,
072 C extends Comparable<? super C>
073 >
074 extends TreeCrossover<G, C>
075 {
076
077 public SingleNodeCrossover(double probability) {
078 super(probability);
079 }
080
081 public SingleNodeCrossover() {
082 this(DEFAULT_ALTER_PROBABILITY);
083 }
084
085 @Override
086 protected <A> int crossover(final TreeNode<A> that, final TreeNode<A> other) {
087 return swap(that, other);
088 }
089
090 // The static method makes it easier to test.
091 static <A> int swap(final TreeNode<A> that, final TreeNode<A> other) {
092 assert that != null;
093 assert other != null;
094
095 final var random = RandomRegistry.random();
096
097 final ISeq<TreeNode<A>> seq1 = that.breadthFirstStream()
098 .collect(ISeq.toISeq());
099
100 final ISeq<TreeNode<A>> seq2 = other.breadthFirstStream()
101 .collect(ISeq.toISeq());
102
103 final int changed;
104 if (seq1.length() > 1 && seq2.length() > 1) {
105 final TreeNode<A> n1 = seq1.get(random.nextInt(seq1.length() - 1) + 1);
106 final TreeNode<A> p1 = n1.parent().orElseThrow(AssertionError::new);
107
108 final TreeNode<A> n2 = seq2.get(random.nextInt(seq2.length() - 1) + 1);
109 final TreeNode<A> p2 = n2.parent().orElseThrow(AssertionError::new);
110
111 final int i1 = p1.indexOf(n1);
112 final int i2 = p2.indexOf(n2);
113
114 p1.insert(i1, n2.detach());
115 p2.insert(i2, n1.detach());
116
117 changed = 2;
118 } else {
119 changed = 0;
120 }
121
122 return changed;
123 }
124
125 @Override
126 public String toString() {
127 return format("SingleNodeCrossover[%f]", _probability);
128 }
129
130 }
|