001 /*
002 * Java Genetic Algorithm Library (jenetics-4.2.0).
003 * Copyright (c) 2007-2018 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 java.util.Random;
023
024 import io.jenetics.Chromosome;
025 import io.jenetics.Gene;
026 import io.jenetics.Mutator;
027 import io.jenetics.MutatorResult;
028 import io.jenetics.internal.math.probability;
029 import io.jenetics.util.ISeq;
030
031 import io.jenetics.ext.util.FlatTree;
032 import io.jenetics.ext.util.FlatTreeNode;
033 import io.jenetics.ext.util.TreeNode;
034
035 /**
036 * Abstract class for mutating tree chromosomes.
037 *
038 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
039 * @version 4.1
040 * @since 4.1
041 */
042 public abstract class TreeMutator<
043 A,
044 G extends TreeGene<A, G>,
045 C extends Comparable<? super C>
046 >
047 extends Mutator<G, C>
048 {
049 public TreeMutator() {
050 this(DEFAULT_ALTER_PROBABILITY);
051 }
052
053 public TreeMutator(final double probability) {
054 super(probability);
055 }
056
057
058 /**
059 * Mutates the given chromosome.
060 *
061 * @see #mutate(Gene, Random)
062 *
063 * @param chromosome the chromosome to mutate
064 * @param p the mutation probability for the underlying genetic objects
065 * @param random the random engine used for the genotype mutation
066 * @return the mutation result
067 */
068 @Override
069 protected MutatorResult<Chromosome<G>> mutate(
070 final Chromosome<G> chromosome,
071 final double p,
072 final Random random
073 ) {
074 final int P = probability.toInt(p);
075 return random.nextInt() < P
076 ? mutate(chromosome)
077 : MutatorResult.of(chromosome);
078 }
079
080 private MutatorResult<Chromosome<G>> mutate(final Chromosome<G> chromosome) {
081 final TreeNode<A> tree = TreeNode.ofTree(chromosome.getGene());
082 mutate(tree);
083
084 final FlatTreeNode<A> flat = FlatTreeNode.of(tree);
085 final ISeq<G> genes = flat.map(t -> gene(chromosome.getGene(), t));
086 return MutatorResult.of(chromosome.newInstance(genes), 1);
087 }
088
089 private G gene(
090 final G template,
091 final FlatTree<? extends A, ?> tree
092 ) {
093 return template.newInstance(
094 tree.getValue(),
095 tree.childOffset(),
096 tree.childCount()
097 );
098 }
099
100 /**
101 * This method does the actual mutating, in place.
102 *
103 * @param tree the mutable tree to mutate
104 */
105 protected abstract void mutate(final TreeNode<A> tree);
106
107 }
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