01 /*
02 * Java Genetic Algorithm Library (jenetics-5.1.0).
03 * Copyright (c) 2007-2019 Franz Wilhelmstötter
04 *
05 * Licensed under the Apache License, Version 2.0 (the "License");
06 * you may not use this file except in compliance with the License.
07 * You may obtain a copy of the License at
08 *
09 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 *
17 * Author:
18 * Franz Wilhelmstötter (franz.wilhelmstoetter@gmail.com)
19 */
20 package io.jenetics.engine;
21
22 import io.jenetics.Gene;
23 import io.jenetics.Phenotype;
24 import io.jenetics.util.ISeq;
25 import io.jenetics.util.Seq;
26
27 /**
28 * This interface allows to define different strategies for evaluating the
29 * fitness functions of a given population. <em>Normally</em>, there is no
30 * need for <em>overriding</em> the default evaluation strategy, but it might
31 * be necessary if you have performance problems and a <em>batched</em>
32 * fitness evaluation would solve the problem.
33 * <p>
34 * The implementer is free to do the evaluation <em>in place</em>, or create
35 * new {@link Phenotype} instance and return the newly created one. A simple
36 * serial evaluator can easily implemented:
37 *
38 * <pre>{@code
39 * final Function<? super Genotype<G>, ? extends C> fitness = ...;
40 * final Evaluator<G, C> evaluator = population -> population
41 * .map(pt -> pt.eval(fitness))
42 * .asISeq();
43 *
44 * final Engine<G, C> engine = new Engine.Builder(evaluator, genotypeFactory)
45 * .build();
46 * }</pre>
47 *
48 * @apiNote
49 * The size of the returned, evaluated, phenotype sequence must be exactly
50 * the size of the input phenotype sequence and all phenotypes must have a
51 * fitness value assigned ({@code assert population.forAll(Phenotype::isEvaluated);}).
52 * It is allowed to return the input sequence, after evaluation, as well a newly
53 * created one.
54 *
55 * @see Evaluators
56 * @see Engine
57 *
58 * @param <G> the gene type
59 * @param <C> the fitness result type
60 *
61 * @author <a href="mailto:franz.wilhelmstoetter@gmail.com">Franz Wilhelmstötter</a>
62 * @version 5.0
63 * @since 4.2
64 */
65 @FunctionalInterface
66 public interface Evaluator<
67 G extends Gene<?, G>,
68 C extends Comparable<? super C>
69 > {
70
71 /**
72 * Evaluates the fitness values of the given {@code population}. The
73 * given {@code population} might contain already evaluated individuals.
74 * It is the responsibility of the implementer to filter out already
75 * evaluated individuals, if desired.
76 *
77 * @param population the population to evaluate
78 * @return the evaluated population. Implementers are free to return the
79 * the input population or a newly created one.
80 */
81 public ISeq<Phenotype<G, C>> eval(final Seq<Phenotype<G, C>> population);
82
83 }
|