1 package net.bmahe.genetics4j.core.replacement;
2
3 import java.util.List;
4 import java.util.Objects;
5
6 import org.apache.commons.lang3.Validate;
7 import org.apache.logging.log4j.LogManager;
8 import org.apache.logging.log4j.Logger;
9
10 import net.bmahe.genetics4j.core.Genotype;
11 import net.bmahe.genetics4j.core.Population;
12 import net.bmahe.genetics4j.core.selection.Selector;
13 import net.bmahe.genetics4j.core.spec.AbstractEAConfiguration;
14 import net.bmahe.genetics4j.core.spec.replacement.Elitism;
15
16 public class ElitismImpl<T extends Comparable<T>> implements ReplacementStrategyImplementor<T> {
17 final static public Logger logger = LogManager.getLogger(ElitismImpl.class);
18
19 private final Elitism elitismSpec;
20 private final Selector<T> offspringSelector;
21 private final Selector<T> survivorSelector;
22
23 public ElitismImpl(final Elitism _elistismSpec, final Selector<T> _offspringSelector,
24 final Selector<T> _survivorSelector) {
25 Objects.requireNonNull(_elistismSpec);
26 Objects.requireNonNull(_offspringSelector);
27 Objects.requireNonNull(_survivorSelector);
28
29 this.elitismSpec = _elistismSpec;
30 this.offspringSelector = _offspringSelector;
31 this.survivorSelector = _survivorSelector;
32 }
33
34 @Override
35 public Population<T> select(final AbstractEAConfiguration<T> eaConfiguration, final long generation,
36 final int numIndividuals, final List<Genotype> population, final List<T> populationScores,
37 final List<Genotype> offsprings, final List<T> offspringScores) {
38 Objects.requireNonNull(eaConfiguration);
39 Validate.isTrue(generation >= 0);
40 Validate.isTrue(numIndividuals > 0);
41 Objects.requireNonNull(population);
42 Objects.requireNonNull(populationScores);
43 Validate.isTrue(population.size() == populationScores.size());
44 Objects.requireNonNull(offsprings);
45 Objects.requireNonNull(offspringScores);
46 Validate.isTrue(offsprings.size() == offspringScores.size());
47 Validate.isTrue(elitismSpec.atLeastNumOffsprings() + elitismSpec.atLeastNumSurvivors() <= numIndividuals);
48
49 final int scaledOffspring = (int) (elitismSpec.offspringRatio() * numIndividuals);
50 final int offspringNeeded = Math.max(scaledOffspring, elitismSpec.atLeastNumOffsprings());
51 final int survivorNeeded = numIndividuals - offspringNeeded;
52
53 final int adjustedOffspringNeeded;
54 final int adjustedSurvivorNeeded;
55 if (survivorNeeded < elitismSpec.atLeastNumSurvivors()) {
56
57 adjustedOffspringNeeded = offspringNeeded - (elitismSpec.atLeastNumSurvivors() - survivorNeeded);
58 adjustedSurvivorNeeded = elitismSpec.atLeastNumSurvivors();
59 } else {
60 adjustedOffspringNeeded = offspringNeeded;
61 adjustedSurvivorNeeded = survivorNeeded;
62 }
63
64 logger.debug("We have {} individuals requested and an offspring ratio of {}. Survivors:{}, Offsprings:{}",
65 numIndividuals,
66 elitismSpec.offspringRatio(),
67 adjustedSurvivorNeeded,
68 adjustedOffspringNeeded);
69
70 final Population<T> selected = new Population<>();
71
72 logger.info("Selecting {} offsprings", adjustedOffspringNeeded);
73 final Population<T> selectedOffspring = offspringSelector
74 .select(eaConfiguration, generation, adjustedOffspringNeeded, offsprings, offspringScores);
75 selected.addAll(selectedOffspring);
76
77 logger.info("Selecting {} survivors", adjustedSurvivorNeeded);
78 final Population<T> selectedSurvivors = survivorSelector
79 .select(eaConfiguration, generation, adjustedSurvivorNeeded, population, populationScores);
80 selected.addAll(selectedSurvivors);
81
82 return selected;
83 }
84 }