/*
 *  RapidMiner
 *
 *  Copyright (C) 2001-2014 by RapidMiner and the contributors
 *
 *  Complete list of developers available at our web site:
 *
 *       http://rapidminer.com
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Affero General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Affero General Public License for more details.
 *
 *  You should have received a copy of the GNU Affero General Public License
 *  along with this program.  If not, see http://www.gnu.org/licenses/.
 */
package com.rapidminer.tools.math.optimization.ec.es;

import java.util.LinkedList;
import java.util.List;
import java.util.Random;

/**
 * Selects a given fixed number of individuals by uniformly sampling from the
 * current population until the desired population size is reached.
 * 
 * @author Ingo Mierswa
 */
public class UniformSelection implements PopulationOperator {

	private int popSize;

	private boolean keepBest;

    private Random random;
    
    
	public UniformSelection(int popSize, boolean keepBest, Random random) {
		this.popSize = popSize;
		this.keepBest = keepBest;
        this.random = random;
	}

	/** The default implementation returns true for every generation. */
	public boolean performOperation(int generation) {
		return true;
	}

	public void operate(Population population) {
		List<Individual> newGeneration = new LinkedList<Individual>();

		if (keepBest) {
			newGeneration.add(population.getBestEver());
		}

		while (newGeneration.size() < popSize) {
			newGeneration.add(population.get(random.nextInt(population.getNumberOfIndividuals())));
		}

		population.clear();
		population.addAll(newGeneration);
	}
}