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// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.searchlib.mlr.ga;
import com.yahoo.searchlib.rankingexpression.RankingExpression;
import java.util.ArrayList;
import java.util.List;
/**
* A species is a population of evolvables.
* Contrary to a real species, a species population may contain (sub)species
* rather than individuals - at all levels but the lowest.
*
* @author <a href="mailto:bratseth@yahoo-inc.com">Jon Bratseth</a>
*/
public class Species extends Evolvable {
private SpeciesName name;
private final Population population;
/** Create a species having a given initial population */
public Species(SpeciesName name, Population population) {
this.name = name;
this.population = population;
}
/** Create a species evolved from a predecessor species, using the given gene pool for mutating it */
private Species(SpeciesName name, Species predecessor, List<RankingExpression> genepool, TrainingEnvironment environment) {
this.name = name;
environment.tracker().newSpecies(predecessor, environment.parameters().getInitialSpeciesSize(), genepool);
// Initialize new species with members generated from the predecessor species
List<Evolvable> initialMembers = new ArrayList<>();
for (int i = 0; i < environment.parameters().getInitialSpeciesSize(); i++)
initialMembers.add(drawFrom(predecessor.population, i).makeSuccessor(i, genepool, environment));
population = new Population(initialMembers);
// Evolve the population of this species for the configured number of generations
environment.tracker().newSpeciesCreated(this);
for (int generation = 0; generation < environment.parameters().getSpeciesLifespan(); generation++) {
environment.tracker().iteration(this, generation+1);
population.evolve(generation, environment);
if (Double.isInfinite(bestIndividual().getFitness())) break; // jackpot
// if (keyboardChecker.isQPressed()) break; // user quit TODO: Make work
}
environment.tracker().speciesCompleted(this);
}
/**
* Draws a member from the given population, where the probability of being drawn is proportional to the
* fitness of the member
*/
private Evolvable drawFrom(Population population, int succession) {
return population.members().get(Math.min(succession % 3, population.members().size() - 1)); // TODO: Probabilistic by fitness?
}
public SpeciesName name() { return name; }
/** The fitness of the fittest individual in the population */
@Override
public double getFitness() {
return population.best().getFitness();
}
/** Creates the successor of this, using its genes, mutated drawing from the given gene pool */
@Override
public Evolvable makeSuccessor(int memberNumber, List<RankingExpression> genepool, TrainingEnvironment environment) {
return new Species(name.successor(memberNumber), this, genepool, environment);
}
/** Returns the members of this species */
public Population population() { return population; }
/** The genes of the fittest individual in the population of this */
@Override
public RankingExpression getGenepool() { // TODO: Less sharp?
return population.best().getGenepool();
}
/** Returns the best individual below this in the species hierarchy (e.g recursively the best leaf) */
public Individual bestIndividual() {
Evolvable child = this;
while (child instanceof Species)
child = ((Species)child).population.best();
return (Individual)child; // it is when it is not instanceof Species
}
@Override
public String toString() {
return "species " + name + ", best member: " + population.best();
}
}
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