Simplify MOEA for continious optimization

[jenetics]

The current classes for MOEA are optimized for a one-time optimization.

final var result = engine.stream()
	.limit(100)
	.collect(MOEA.toParetoSet(IntRange.of(20, 25)))

If you want to have intermediate results, the effort to do so is a little bit to much for an average library user.

public void evolve(final Subscriber<Result> subscriber) {
	final ParetoFront<Phenotype<DoubleGene, Vec<double[]>>> best =
		new ParetoFront<>(this::dominance, this::equals);

	final var stream = _engine.stream()
		.limit(r -> Thread.currentThread().isInterrupted())
		.peek(r -> add(best, IntRange.of(30, 50), r))
		.map(r -> new Result(r, List.copyOf(best)));

	final var publisher = new StreamPublisher<Result>();
	publisher.subscribe(subscriber);
	publisher.attach(stream);
}

private void add(
	final ParetoFront<Phenotype<DoubleGene, Vec<double[]>>> best,
	final IntRange size,
	final EvolutionResult<DoubleGene, Vec<double[]>> result
) {
	final ISeq<Phenotype<DoubleGene, Vec<double[]>>> front = front(
		result.population(),
		this::dominance
	);
	best.addAll(front.asList());
	trim(best, size);
}

private int dominance(
	final Phenotype<DoubleGene, Vec<double[]>> a,
	final Phenotype<DoubleGene, Vec<double[]>> b
) {
	return Pareto.dominance(a.fitness().data(), b.fitness().data());
}

private boolean equals(final Phenotype<?, ?> a, final Phenotype<?, ?> b) {
	return Objects.equals(a.genotype(), b.genotype());
}

private void trim(
	final ParetoFront<Phenotype<DoubleGene, Vec<double[]>>> best,
	final IntRange size
) {
	if (best.size() > size.max() - 1) {
		best.trim(
			size.min(),
			this::compare,
			this::distance,
			v -> v.fitness().length()
		);
	}
}

private int compare(
	final Phenotype<DoubleGene, Vec<double[]>> a,
	final Phenotype<DoubleGene, Vec<double[]>> b,
	final int i
) {
	return a.fitness().compare(b.fitness(), i);
}

private double distance(
	final Phenotype<DoubleGene, Vec<double[]>> a,
	final Phenotype<DoubleGene, Vec<double[]>> b,
	final int i
) {
	return a.fitness().distance(b.fitness(), i);
}

[jenetics]

Merged into r6.1.0 branch.