001 /*
002 * Java Genetic Algorithm Library (jenetics-4.1.0).
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.engine;
021
022 import static java.util.Objects.requireNonNull;
023
024 import java.util.function.Function;
025
026 import io.jenetics.Gene;
027 import io.jenetics.Genotype;
028
029 /**
030 * This interface describes a <i>problem</i> which can be solved by the GA
031 * evolution {@code Engine}. It connects the actual {@link #fitness()} function
032 * and the needed {@link #codec()}.
033 *
034 * <pre>{@code
035 * final Problem<ISeq<BitGene>, BitGene, Integer> counting = Problem.of(
036 * // Native fitness function
037 * genes -> (int)genes.stream()
038 * .filter(BitGene::getBit)
039 * .count(),
040 * // Problem encoding
041 * Codec.of(
042 * Genotype.of(BitChromosome.of(100)),
043 * gt -> gt.getChromosome().toSeq()
044 * )
045 * );
046 * }</pre>
047 *
048 * The example above shows the Ones-Counting problem definition.
049 *
050 * @see Codec
051 * @see Engine
052 *
053 * @param <T> the (<i>native</i>) argument type of the problem fitness function
054 * @param <G> the gene type the evolution engine is working with
055 * @param <C> the result type of the fitness function
056 *
057 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
058 * @version 4.1
059 * @since 3.4
060 */
061 public interface Problem<
062 T,
063 G extends Gene<?, G>,
064 C extends Comparable<? super C>
065 > {
066
067 /**
068 * Return the fitness function of the <i>problem</i> in the <i>native</i>
069 * problem domain.
070 *
071 * @return the fitness function
072 */
073 public Function<T, C> fitness();
074
075 /**
076 * Return the codec, which translates the types of the problem domain into
077 * types, which can be understand by the evolution {@code Engine}.
078 *
079 * @return the engine codec
080 */
081 public Codec<T, G> codec();
082
083 /**
084 * Returns the fitness value for the given argument.
085 *
086 * @since 4.1
087 *
088 * @param arg the argument of the fitness function
089 * @return the fitness value
090 */
091 public default C fitness(final T arg) {
092 return fitness().apply(arg);
093 }
094
095 /**
096 * Returns the fitness value for the given argument.
097 *
098 * @since 4.1
099 *
100 * @param gt the argument of the fitness function
101 * @return the fitness value
102 */
103 public default C fitness(final Genotype<G> gt) {
104 return fitness(codec().decode(gt));
105 }
106
107 /**
108 * Return a new optimization <i>problem</i> with the given parameters.
109 *
110 * @param fitness the problem fitness function
111 * @param codec the evolution engine codec
112 * @param <T> the (<i>native</i>) argument type of the problem fitness function
113 * @param <G> the gene type the evolution engine is working with
114 * @param <C> the result type of the fitness function
115 * @return a new problem object from the given parameters
116 * @throws NullPointerException if one of the arguments is {@code null}
117 */
118 public static <T, G extends Gene<?, G>, C extends Comparable<? super C>>
119 Problem<T, G, C> of(
120 final Function<T, C> fitness,
121 final Codec<T, G> codec
122 ) {
123 requireNonNull(fitness);
124 requireNonNull(codec);
125
126 return new Problem<T, G, C>() {
127 @Override
128 public Codec<T, G> codec() {
129 return codec;
130 }
131
132 @Override
133 public Function<T, C> fitness() {
134 return fitness;
135 }
136 };
137 }
138
139 }
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