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.engine;
021
022 import static java.lang.String.format;
023 import static java.util.Objects.requireNonNull;
024 import static io.jenetics.internal.util.Hashes.hash;
025
026 import java.util.Objects;
027
028 import io.jenetics.Gene;
029 import io.jenetics.Phenotype;
030 import io.jenetics.internal.util.require;
031 import io.jenetics.util.ISeq;
032
033 /**
034 * Represents a state of the GA at the start of an evolution step.
035 *
036 * @see EvolutionResult
037 * @see EvolutionInit
038 * @see EvolutionStreamable#stream(EvolutionStart)
039 *
040 * @param <G> the gene type
041 * @param <C> the fitness type
042 *
043 * @implNote
044 * This class is immutable and thread-safe.
045 *
046 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
047 * @since 3.1
048 * @version 5.1
049 */
050 public final class EvolutionStart<
051 G extends Gene<?, G>,
052 C extends Comparable<? super C>
053 > {
054
055 private final ISeq<Phenotype<G, C>> _population;
056 private final long _generation;
057
058 private EvolutionStart(
059 final ISeq<Phenotype<G, C>> population,
060 final long generation
061 ) {
062 _population = requireNonNull(population);
063 _generation = require.positive(generation);
064 }
065
066 /**
067 * Return the population before the evolution step.
068 *
069 * @return the start population
070 */
071 public ISeq<Phenotype<G, C>> getPopulation() {
072 return _population;
073 }
074
075 /**
076 * Return the generation of the start population.
077 *
078 * @return the start generation
079 */
080 public long getGeneration() {
081 return _generation;
082 }
083
084 @Override
085 public int hashCode() {
086 return hash(_generation, hash(_population, hash(getClass())));
087 }
088
089 @Override
090 public boolean equals(final Object obj) {
091 return obj == this ||
092 obj instanceof EvolutionStart &&
093 _generation == ((EvolutionStart)obj)._generation &&
094 Objects.equals(_population, ((EvolutionStart)obj)._population);
095 }
096
097 @Override
098 public String toString() {
099 return format(
100 "EvolutionStart[population-size=%d, generation=%d]",
101 _population.size(), _generation
102 );
103 }
104
105 /**
106 * Create a new evolution start object with the given population and for the
107 * given generation.
108 *
109 * @param <G> the gene type
110 * @param <C> the fitness type
111 * @param population the start population.
112 * @param generation the start generation of the population
113 * @return a new evolution start object
114 * @throws java.lang.NullPointerException if the given {@code population} is
115 * {@code null}.
116 * @throws IllegalArgumentException if the given {@code generation} is
117 * smaller then one
118 */
119 public static <G extends Gene<?, G>, C extends Comparable<? super C>>
120 EvolutionStart<G, C> of(
121 final ISeq<Phenotype<G, C>> population,
122 final long generation
123 ) {
124 return new EvolutionStart<>(population, generation);
125 }
126
127 /**
128 * An empty evolution start object, which can be used as initial evolution
129 * value. The evolution {@link Engine} is then responsible for creating the
130 * proper initial population,
131 *
132 * @since 5.1
133 *
134 * @param <G> the gene type
135 * @param <C> the fitness type
136 * @return an empty evolution start object
137 */
138 public static <G extends Gene<?, G>, C extends Comparable<? super C>>
139 EvolutionStart<G, C> empty() {
140 return new EvolutionStart<>(ISeq.empty(), 1);
141 }
142
143 }
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