/* -*- tab-width: 4 -*-
*
* Electric(tm) VLSI Design System
*
* File: SelectionTournament.java
* Written by Team 3: Christian Wittner
*
* This code has been developed at the Karlsruhe Institute of Technology (KIT), Germany,
* as part of the course "Multicore Programming in Practice: Tools, Models, and Languages".
* Contact instructor: Dr. Victor Pankratius (pankratius@ipd.uka.de)
*
* Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
*
* Electric(tm) is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* Electric(tm) 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Electric(tm); see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
* Boston, Mass 02111-1307, USA.
*/
package com.sun.electric.tool.placement.genetic1.g1;
import com.sun.electric.tool.placement.genetic1.Chromosome;
import com.sun.electric.tool.placement.genetic1.Population;
import com.sun.electric.tool.placement.genetic1.Selection;
import java.util.List;
/**
* Imitate a tournament. Randomly pick to individuals to compete. The weaker one
* gets sorted out.
*
* This way a weak solution has a chance of survival and the strongest one never
* gets dropped.
*/
public class SelectionTournament implements Selection {
public void selection(Population population) {
Chromosome a, b;
List<Chromosome> chromsomes = population.chromosomes;
// as long as we have two many individuals
while (chromsomes.size() > GeneticPlacement.current_population_size_per_thread) {
// select two individuals
a = chromsomes.get(population.getRandomGenerator().nextInt(
chromsomes.size()));
b = a;
while (a == b) {
b = chromsomes.get(population.getRandomGenerator().nextInt(
chromsomes.size()));
}
// remove the weaker one with the longer wire length
if (a.fitness.doubleValue() > b.fitness.doubleValue()) {
chromsomes.remove(a);
} else {
chromsomes.remove(b);
}
}
}
}