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MATH-1618: Make "stopping condition" a "BiPredicate". 

Second argument is the generation count (as determined by the caller).
This commit is contained in:
Gilles Sadowski 2022-06-12 02:41:56 +02:00
parent f0fe9ab8eb
commit 383256f8cf
3 changed files with 27 additions and 17 deletions
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4
commons-math-examples/examples-ga/examples-ga-math-functions/src/main/java/org/apache/commons/math4/examples/ga/mathfunctions/MathFunctionOptimizer2.java
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@ -23,7 +23,7 @@ import java.util.HashMap;
import java.util.List;
import java.util.function.Function;
import java.util.function.ToDoubleFunction;
import java.util.function.Predicate;
import java.util.function.BiPredicate;
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Callable;
@ -100,7 +100,7 @@ public final class MathFunctionOptimizer2 {
};
// Stopping condition (not thread-safe).
final Predicate<Population<Chromosome, Coordinates>> stop =
final BiPredicate<Population<Chromosome, Coordinates>, Integer> stop =
new UnchangedFitness(UnchangedFitness.Type.BEST,
numGeneration);

13
commons-math-ga2/src/main/java/org/apache/commons/math4/ga2/GeneticAlgorithmFactory.java
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@ -23,7 +23,7 @@ import java.util.ArrayList;
import java.util.Map;
import java.util.concurrent.Callable;
import java.util.function.Function;
import java.util.function.Predicate;
import java.util.function.BiPredicate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.apache.commons.rng.simple.RandomSource;
@ -43,7 +43,7 @@ public final class GeneticAlgorithmFactory<G, P> implements Callable<Population<
/** Genotype to phenotype converter. */
private final Function<G, P> decoder;
/** Criterion for stopping the evolution. */
private final Predicate<Population<G, P>> stop;
private final BiPredicate<Population<G, P>, Integer> stop;
/** Fitness calculator. */
private final FitnessService<G, P> fitness;
/** Chromosome selector. */
@ -71,7 +71,7 @@ public final class GeneticAlgorithmFactory<G, P> implements Callable<Population<
*/
private GeneticAlgorithmFactory(Collection<G> init,
Function<G, P> decoder,
Predicate<Population<G, P>> stop,
BiPredicate<Population<G, P>, Integer> stop,
FitnessService<G, P> fitness,
Selection<G, P> selection,
Map<GeneticOperator<G>, ApplicationRate> operators,
@ -107,7 +107,7 @@ public final class GeneticAlgorithmFactory<G, P> implements Callable<Population<
*/
public static <G, P> Callable<Population<G, P>> create(Collection<G> init,
Function<G, P> decoder,
Predicate<Population<G, P>> stop,
BiPredicate<Population<G, P>, Integer> stop,
FitnessService<G, P> fitness,
Selection<G, P> selection,
Map<GeneticOperator<G>, ApplicationRate> operators,
@ -147,7 +147,7 @@ public final class GeneticAlgorithmFactory<G, P> implements Callable<Population<
ChromosomeFactory<G> initFactory,
int populationSize,
Function<G, P> decoder,
Predicate<Population<G, P>> stop,
BiPredicate<Population<G, P>, Integer> stop,
FitnessService<G, P> fitness,
Selection<G, P> selection,
Map<GeneticOperator<G>, ApplicationRate> operators,
@ -181,8 +181,7 @@ public final class GeneticAlgorithmFactory<G, P> implements Callable<Population<
currentGen.add(init);
final UniformRandomProvider rng = random.create();
while (!stop.test(currentGen)) {
++generation;
while (!stop.test(currentGen, ++generation)) {
final Population<G, P> nextGen = new Population<>(popSize, decoder, fitness);
applyElitism(currentGen, nextGen);

27
commons-math-ga2/src/main/java/org/apache/commons/math4/ga2/stop/UnchangedFitness.java
View File

@ -18,25 +18,30 @@ package org.apache.commons.math4.ga2.stop;
import java.util.Map;
import java.util.function.ToDoubleFunction;
import java.util.function.Predicate;
import java.util.function.BiPredicate;
import org.apache.commons.math4.ga2.Population;
/**
* Criterion for asserting convergence of a population.
* Note: Class is <em>not</em> thread-safe.
* Notes:
* <ul>
* <li>Class is <em>not</em> thread-safe.</li>
* <li>A <em>new</em> instance must created for each GA run (otherwise
* an {@link IllegalStateException} will be thrown).</li>
* </ul>
*
* @param <G> Genotype.
* @param <P> Phenotype.
*/
public class UnchangedFitness<G, P> implements Predicate<Population<G, P>> {
public class UnchangedFitness<G, P> implements BiPredicate<Population<G, P>, Integer> {
/** Function that computes the reference value. */
private final ToDoubleFunction<Population<G, P>> calculator;
/** Number of generations during which no change has happened. */
private final int maxGenerations;
/** Value for previous population. */
private double previousFitness = Double.NaN;
/** Number of generations without changes. */
private int generations = 0;
/** Generation at which the last change has occurred. */
private int updatedGeneration = 0;
/** What needs to be unchanged. */
public enum Type {
@ -71,14 +76,20 @@ public class UnchangedFitness<G, P> implements Predicate<Population<G, P>> {
/** {@inheritDoc} */
@Override
public boolean test(Population<G, P> population) {
public boolean test(Population<G, P> population,
Integer generationCounter) {
final int genDiff = generationCounter - updatedGeneration;
if (genDiff < 0) {
throw new IllegalStateException("Incorrect usage");
}
final double fitness = calculator.applyAsDouble(population);
if (fitness == previousFitness) {
if (++generations > maxGenerations) {
if (genDiff > maxGenerations) {
return true;
}
} else {
generations = 0;
updatedGeneration = generationCounter;
previousFitness = fitness;
}