// Filters out invalid and to old individuals. Filtering is done in place.
private FilterResult<G, C> filter(final Population<G, C> population, final long generation) {
int killCount = 0;
int invalidCount = 0;
for (int i = 0, n = population.size(); i < n; ++i) {
final Phenotype<G, C> individual = population.get(i);
if (!_validator.test(individual)) {
population.set(i, newPhenotype(generation));
++invalidCount;
} else if (individual.getAge(generation) > _maximalPhenotypeAge) {
population.set(i, newPhenotype(generation));
++killCount;
}
}
return new FilterResult<>(population, killCount, invalidCount);
}
private EvolutionStart<G, C> evolutionStart(
final Population<G, C> population, final long generation) {
final Stream<Phenotype<G, C>> stream =
Stream.concat(
population
.stream()
.map(p -> p.newInstance(p.getGeneration(), _fitnessFunction, _fitnessScaler)),
Stream.generate(() -> newPhenotype(generation)));
final Population<G, C> pop = stream.limit(getPopulationSize()).collect(toPopulation());
return EvolutionStart.of(pop, generation);
}
// Selects the offspring population. A new population object is returned.
private Population<G, C> selectOffspring(final Population<G, C> population) {
return _offspringCount > 0
? _offspringSelector.select(population, _offspringCount, _optimize)
: Population.empty();
}
// Selects the survivors population. A new population object is returned.
private Population<G, C> selectSurvivors(final Population<G, C> population) {
return _survivorsCount > 0
? _survivorsSelector.select(population, _survivorsCount, _optimize)
: Population.empty();
}
/**
* Perform one evolution step with the given evolution {@code start} object New phenotypes are
* created with the fitness function and fitness scaler defined by this <em>engine</em>
*
* <p><em>This method is thread-safe.</em>
*
* @since 3.1
* @see #evolve(org.jenetics.Population, long)
* @param start the evolution start object
* @return the evolution result
* @throws java.lang.NullPointerException if the given evolution {@code start} is {@code null}
*/
public EvolutionResult<G, C> evolve(final EvolutionStart<G, C> start) {
final Timer timer = Timer.of().start();
final Population<G, C> startPopulation = start.getPopulation();
// Initial evaluation of the population.
final Timer evaluateTimer = Timer.of(_clock).start();
evaluate(startPopulation);
evaluateTimer.stop();
// Select the offspring population.
final CompletableFuture<TimedResult<Population<G, C>>> offspring =
_executor.async(() -> selectOffspring(startPopulation), _clock);
// Select the survivor population.
final CompletableFuture<TimedResult<Population<G, C>>> survivors =
_executor.async(() -> selectSurvivors(startPopulation), _clock);
// Altering the offspring population.
final CompletableFuture<TimedResult<AlterResult<G, C>>> alteredOffspring =
_executor.thenApply(offspring, p -> alter(p.result, start.getGeneration()), _clock);
// Filter and replace invalid and to old survivor individuals.
final CompletableFuture<TimedResult<FilterResult<G, C>>> filteredSurvivors =
_executor.thenApply(survivors, pop -> filter(pop.result, start.getGeneration()), _clock);
// Filter and replace invalid and to old offspring individuals.
final CompletableFuture<TimedResult<FilterResult<G, C>>> filteredOffspring =
_executor.thenApply(
alteredOffspring, pop -> filter(pop.result.population, start.getGeneration()), _clock);
// Combining survivors and offspring to the new population.
final CompletableFuture<Population<G, C>> population =
filteredSurvivors.thenCombineAsync(
filteredOffspring,
(s, o) -> {
final Population<G, C> pop = s.result.population;
pop.addAll(o.result.population);
return pop;
},
_executor.get());
// Evaluate the fitness-function and wait for result.
final Population<G, C> pop = population.join();
final TimedResult<Population<G, C>> result = TimedResult.of(() -> evaluate(pop), _clock).get();
final EvolutionDurations durations =
EvolutionDurations.of(
offspring.join().duration,
survivors.join().duration,
alteredOffspring.join().duration,
filteredOffspring.join().duration,
filteredSurvivors.join().duration,
result.duration.plus(evaluateTimer.getTime()),
timer.stop().getTime());
final int killCount =
filteredOffspring.join().result.killCount + filteredSurvivors.join().result.killCount;
final int invalidCount =
filteredOffspring.join().result.invalidCount + filteredSurvivors.join().result.invalidCount;
return EvolutionResult.of(
_optimize,
result.result,
start.getGeneration(),
durations,
killCount,
invalidCount,
alteredOffspring.join().result.alterCount);
}
private static Population<DoubleGene, Double> population(final int min, final int max) {
return IntStream.rangeClosed(min, max)
.mapToDouble(i -> (double) i)
.mapToObj(FitnessThresholdLimitTest::phenotype)
.collect(Population.toPopulation());
}