01 /*
02 * Java Genetic Algorithm Library (jenetics-3.0.0).
03 * Copyright (c) 2007-2014 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@gmx.at)
19 */
20 package org.jenetics.engine;
21
22 import java.util.function.Predicate;
23
24 import org.jenetics.internal.util.require;
25
26 /**
27 * This class contains factory methods for creating predicates, which can be
28 * used for limiting the evolution stream.
29 *
30 * @see EvolutionStream#limit(Predicate)
31 *
32 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
33 * @since 3.0
34 * @version 3.0 — <em>$Date: 2014-12-28 $</em>
35 */
36 public final class limit {
37 private limit() {require.noInstance();}
38
39
40 /**
41 * Return a predicate, which will truncate the evolution stream if no
42 * better phenotype could be found after the given number of
43 * {@code generations}.
44 *
45 * [code]
46 * final Phenotype<DoubleGene, Double> result = engine.stream()
47 * // Truncate the evolution stream after 5 "steady" generations.
48 * .limit(bySteadyFitness(5))
49 * // The evolution will stop after maximal 100 generations.
50 * .limit(100)
51 * .collect(toBestPhenotype());
52 * [/code]
53 *
54 * @param generations the number of <i>steady</i> generations
55 * @param <C> the fitness type
56 * @return a predicate which truncate the evolution stream if no better
57 * phenotype could be found after a give number of
58 * {@code generations}
59 * @throws IllegalArgumentException if the generation is smaller than
60 * one.
61 */
62 public static <C extends Comparable<? super C>>
63 Predicate<EvolutionResult<?, C>> bySteadyFitness(final int generations) {
64 return new SteadyFitnessLimit<>(generations);
65 }
66
67 }
|