1 package net.bmahe.genetics4j.core.selection;
2
3 import java.util.ArrayList;
4 import java.util.Comparator;
5 import java.util.List;
6 import java.util.random.RandomGenerator;
7 import java.util.stream.Collectors;
8
9 import org.apache.commons.lang3.Validate;
10 import org.apache.logging.log4j.LogManager;
11 import org.apache.logging.log4j.Logger;
12
13 import net.bmahe.genetics4j.core.Genotype;
14 import net.bmahe.genetics4j.core.Individual;
15 import net.bmahe.genetics4j.core.Population;
16 import net.bmahe.genetics4j.core.spec.AbstractEAConfiguration;
17 import net.bmahe.genetics4j.core.spec.AbstractEAExecutionContext;
18 import net.bmahe.genetics4j.core.spec.selection.MultiTournaments;
19 import net.bmahe.genetics4j.core.spec.selection.SelectionPolicy;
20 import net.bmahe.genetics4j.core.spec.selection.Tournament;
21
22 public class MultiTournamentsSelectionPolicyHandler<T extends Comparable<T>> implements SelectionPolicyHandler<T> {
23 final static public Logger logger = LogManager.getLogger(MultiTournamentsSelectionPolicyHandler.class);
24
25 private final RandomGenerator randomGenerator;
26
27 private List<Individual<T>> pickRandomCandidates(final RandomGenerator randomGenerator,
28 final List<Genotype> population, final List<T> fitnessScore, final int numCandidates) {
29 Validate.notNull(randomGenerator);
30 Validate.notNull(population);
31 Validate.notNull(fitnessScore);
32 Validate.isTrue(fitnessScore.size() > 0);
33 Validate.isTrue(numCandidates > 0);
34
35 return randomGenerator.ints(0, fitnessScore.size())
36 .boxed()
37 .limit(numCandidates)
38 .map(i -> Individual.of(population.get(i), fitnessScore.get(i)))
39 .collect(Collectors.toList());
40 }
41
42 private Individual<T> runTournament(final Tournament<T> tournament, final List<Genotype> population,
43 final List<T> fitnessScore, final List<Individual<T>> candidates) {
44 Validate.notNull(tournament);
45
46 final Comparator<Individual<T>> comparator = tournament.comparator();
47
48 return candidates.stream()
49 .max(comparator)
50 .get();
51 }
52
53 private Individual<T> runTournament(final RandomGenerator randomGenerator, final List<Tournament<T>> tournaments,
54 final List<Genotype> population, final List<T> fitnessScore, final int tournamentIndex) {
55 Validate.notNull(tournaments);
56 Validate.notNull(population);
57 Validate.notNull(fitnessScore);
58 Validate.isTrue(tournamentIndex < tournaments.size());
59 Validate.isTrue(tournamentIndex >= 0);
60
61 final Tournament<T> tournament = tournaments.get(tournamentIndex);
62 final int numCandidates = tournament.numCandidates();
63
64 List<Individual<T>> candidates;
65 if (tournamentIndex == 0) {
66 candidates = pickRandomCandidates(randomGenerator, population, fitnessScore, numCandidates);
67 } else {
68 candidates = new ArrayList<>();
69
70 for (int i = 0; i < numCandidates; i++) {
71 final Individual<T> candidate = runTournament(randomGenerator,
72 tournaments,
73 population,
74 fitnessScore,
75 tournamentIndex - 1);
76 candidates.add(candidate);
77 }
78 }
79
80 return runTournament(tournament, population, fitnessScore, candidates);
81
82 }
83
84 public MultiTournamentsSelectionPolicyHandler(final RandomGenerator _randomGenerator) {
85 Validate.notNull(_randomGenerator);
86
87 this.randomGenerator = _randomGenerator;
88 }
89
90 @Override
91 public boolean canHandle(final SelectionPolicy selectionPolicy) {
92 Validate.notNull(selectionPolicy);
93 return selectionPolicy instanceof MultiTournaments;
94 }
95
96 @Override
97 public Selector<T> resolve(final AbstractEAExecutionContext<T> eaExecutionContext,
98 final AbstractEAConfiguration<T> eaConfiguration,
99 final SelectionPolicyHandlerResolver<T> selectionPolicyHandlerResolver,
100 final SelectionPolicy selectionPolicy) {
101 Validate.notNull(selectionPolicy);
102 Validate.isInstanceOf(MultiTournaments.class, selectionPolicy);
103
104 return new Selector<T>() {
105
106 @Override
107 public Population<T> select(final AbstractEAConfiguration<T> eaConfiguration, final int numIndividuals,
108 final List<Genotype> population, final List<T> fitnessScore) {
109 Validate.notNull(eaConfiguration);
110 Validate.notNull(population);
111 Validate.notNull(fitnessScore);
112 Validate.isTrue(numIndividuals > 0);
113 Validate.isTrue(population.size() == fitnessScore.size());
114
115 @SuppressWarnings("unchecked")
116 final MultiTournaments<T> multiTournaments = (MultiTournaments<T>) selectionPolicy;
117 final List<Tournament<T>> tournaments = multiTournaments.tournaments();
118
119 logger.debug("Selecting {} individuals", numIndividuals);
120 final Population<T> selectedIndividuals = new Population<>();
121 while (selectedIndividuals.size() < numIndividuals) {
122 final Individual<T> selectedIndividual = runTournament(randomGenerator,
123 tournaments,
124 population,
125 fitnessScore,
126 tournaments.size() - 1);
127 selectedIndividuals.add(selectedIndividual);
128 }
129
130 return selectedIndividuals;
131 }
132 };
133 }
134 }