01 /*
02 * Java Genetic Algorithm Library (jenetics-3.5.0).
03 * Copyright (c) 2007-2016 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 static org.jenetics.stat.DoubleMoments.toDoubleMoments;
23
24 import java.util.function.Predicate;
25
26 import org.jenetics.Optimize;
27 import org.jenetics.stat.DoubleMoments;
28
29 /**
30 * @author <a href="mailto:franz.wilhelmstoetter@gmx.at">Franz Wilhelmstötter</a>
31 * @since 3.0
32 * @version 3.0
33 */
34 final class SteadyPopulationLimit<
35 N extends Number & Comparable<? super N>
36 >
37 implements Predicate<EvolutionResult<?, N>>
38 {
39 private final int _generations;
40 private int _stableGenerations = 0;
41 private N _fitness;
42
43 private SteadyPopulationLimit(final int generations) {
44 _generations = generations;
45 }
46
47 @Override
48 public boolean test(final EvolutionResult<?, N> result) {
49 final DoubleMoments moments = result.getPopulation().stream()
50 .collect(toDoubleMoments(pt -> pt.getFitness().doubleValue()));
51
52 boolean proceed = true;
53
54 if (_fitness == null) {
55 _fitness = result.getBestFitness();
56 _stableGenerations = 1;
57 } else {
58 final Optimize opt = result.getOptimize();
59 if (opt.compare(_fitness, result.getBestFitness()) >= 0) {
60 proceed = ++_stableGenerations <= _generations;
61 } else {
62 _fitness = result.getBestFitness();
63 _stableGenerations = 1;
64 }
65 }
66
67 return proceed;
68 }
69 }
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