001 /*
002 * Java Genetic Algorithm Library (jenetics-5.1.0).
003 * Copyright (c) 2007-2019 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.Mutator;
026 import io.jenetics.MutatorResult;
027 import io.jenetics.internal.math.probability;
028 import io.jenetics.util.ISeq;
029
030 import io.jenetics.ext.util.FlatTree;
031 import io.jenetics.ext.util.FlatTreeNode;
032 import io.jenetics.ext.util.TreeNode;
033
034 /**
035 * Abstract class for mutating tree chromosomes.
036 *
037 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
038 * @version 4.1
039 * @since 4.1
040 */
041 public abstract class TreeMutator<
042 A,
043 G extends TreeGene<A, G>,
044 C extends Comparable<? super C>
045 >
046 extends Mutator<G, C>
047 {
048 public TreeMutator() {
049 this(DEFAULT_ALTER_PROBABILITY);
050 }
051
052 public TreeMutator(final double probability) {
053 super(probability);
054 }
055
056
057 /**
058 * Mutates the given chromosome.
059 *
060 * @param chromosome the chromosome to mutate
061 * @param p the mutation probability for the underlying genetic objects
062 * @param random the random engine used for the genotype mutation
063 * @return the mutation result
064 */
065 @Override
066 protected MutatorResult<Chromosome<G>> mutate(
067 final Chromosome<G> chromosome,
068 final double p,
069 final Random random
070 ) {
071 final int P = probability.toInt(p);
072 return random.nextInt() < P
073 ? mutate(chromosome)
074 : MutatorResult.of(chromosome);
075 }
076
077 private MutatorResult<Chromosome<G>> mutate(final Chromosome<G> chromosome) {
078 final TreeNode<A> tree = TreeNode.ofTree(chromosome.getGene());
079 mutate(tree);
080
081 final FlatTreeNode<A> flat = FlatTreeNode.of(tree);
082 final ISeq<G> genes = flat.map(t -> gene(chromosome.getGene(), t));
083 return MutatorResult.of(chromosome.newInstance(genes), 1);
084 }
085
086 private G gene(
087 final G template,
088 final FlatTree<? extends A, ?> tree
089 ) {
090 return template.newInstance(
091 tree.getValue(),
092 tree.childOffset(),
093 tree.childCount()
094 );
095 }
096
097 /**
098 * This method does the actual mutating, in place.
099 *
100 * @param tree the mutable tree to mutate
101 */
102 protected abstract void mutate(final TreeNode<A> tree);
103
104 }
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