com.ciphertool.genetics.algorithms.ConcurrentBasicGeneticAlgorithm.java Source code

Introduction

Here is the source code for com.ciphertool.genetics.algorithms.ConcurrentBasicGeneticAlgorithm.java

Source

/**
 * Copyright 2012 George Belden
 * 
 * This file is part of ZodiacGenetics.
 * 
 * ZodiacGenetics 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.
 * 
 * ZodiacGenetics 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
 * ZodiacGenetics. If not, see <http://www.gnu.org/licenses/>.
 */

package com.ciphertool.genetics.algorithms;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

import org.apache.log4j.Logger;
import org.springframework.beans.factory.annotation.Required;
import org.springframework.core.task.TaskExecutor;

import com.ciphertool.genetics.entities.Chromosome;

public class ConcurrentBasicGeneticAlgorithm extends BasicGeneticAlgorithm {
    private Logger log = Logger.getLogger(getClass());
    private TaskExecutor taskExecutor;

    /**
     * A concurrent task for performing a crossover of two parent Chromosomes,
     * producing one child Chromosome.
     */
    private class CrossoverTask implements Callable<List<Chromosome>> {

        private Chromosome mom;
        private Chromosome dad;

        public CrossoverTask(Chromosome mom, Chromosome dad) {
            this.mom = mom;
            this.dad = dad;
        }

        @Override
        public List<Chromosome> call() throws Exception {
            return crossoverAlgorithm.crossover(mom, dad);
        }
    }

    /*
     * Crossover algorithm utilizing Roulette Wheel Selection
     * 
     * (non-Javadoc)
     * 
     * @see com.ciphertool.zodiacengine.genetic.GeneticAlgorithm#crossover()
     */
    @Override
    public int crossover(int initialPopulationSize) {
        if (this.population.size() < 2) {
            log.info(
                    "Unable to perform crossover because there is only 1 individual in the population. Returning.");

            return 0;
        }

        long pairsToCrossover = Math.min((long) (initialPopulationSize * strategy.getCrossoverRate()),
                ((long) (this.population.size() / 2)));

        log.debug("Pairs to crossover: " + pairsToCrossover);

        Chromosome mom = null;
        Chromosome dad = null;
        int momIndex = -1;
        int dadIndex = -1;

        List<Chromosome> moms = new ArrayList<Chromosome>();
        List<Chromosome> dads = new ArrayList<Chromosome>();

        /*
         * We first remove all the parent Chromosomes since the children are
         * guaranteed to be at least as fit. This also prevents parents from
         * reproducing more than one time per generation.
         */
        for (int i = 0; i < pairsToCrossover; i++) {
            momIndex = this.population.selectIndex();
            moms.add(this.population.getIndividuals().get(momIndex));
            this.population.makeIneligibleForReproduction(momIndex);

            dadIndex = this.population.selectIndex();
            dads.add(this.population.getIndividuals().get(dadIndex));
            this.population.makeIneligibleForReproduction(dadIndex);
        }

        List<FutureTask<List<Chromosome>>> futureTasks = new ArrayList<FutureTask<List<Chromosome>>>();
        FutureTask<List<Chromosome>> futureTask = null;

        /*
         * Execute each crossover concurrently. Parents should produce two
         * children, but this is not necessarily always guaranteed.
         */
        for (int i = 0; i < pairsToCrossover; i++) {
            mom = moms.get(i);
            dad = dads.get(i);

            futureTask = new FutureTask<List<Chromosome>>(new CrossoverTask(mom, dad));
            futureTasks.add(futureTask);
            this.taskExecutor.execute(futureTask);
        }

        List<Chromosome> childrenToAdd = new ArrayList<Chromosome>();
        /*
         * Add the result of each FutureTask to the population since it
         * represents a new child Chromosome.
         */
        for (FutureTask<List<Chromosome>> future : futureTasks) {
            try {
                /*
                 * Add children after all crossover operations are completed so
                 * that children are not inadvertently breeding immediately
                 * after birth.
                 */
                childrenToAdd.addAll(future.get());
            } catch (InterruptedException ie) {
                log.error("Caught InterruptedException while waiting for CrossoverTask ", ie);
            } catch (ExecutionException ee) {
                log.error("Caught ExecutionException while waiting for CrossoverTask ", ee);
            }
        }

        for (Chromosome child : childrenToAdd) {
            this.population.addIndividualAsIneligible(child);
        }

        return (int) pairsToCrossover;
    }

    /**
     * @param taskExecutor
     *            the taskExecutor to set
     */
    @Required
    public void setTaskExecutor(TaskExecutor taskExecutor) {
        this.taskExecutor = taskExecutor;
    }
}