/*******************************************************************************
* Copyright (C) 2013 Stefan Schroeder
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 3.0 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library. If not, see <http://www.gnu.org/licenses/>.
******************************************************************************/
package jsprit.core.algorithm.acceptor;
import jsprit.core.algorithm.VehicleRoutingAlgorithm;
import jsprit.core.algorithm.io.AlgorithmConfig;
import jsprit.core.algorithm.io.AlgorithmConfigXmlReader;
import jsprit.core.algorithm.io.VehicleRoutingAlgorithms;
import jsprit.core.algorithm.listener.AlgorithmStartsListener;
import jsprit.core.algorithm.listener.IterationEndsListener;
import jsprit.core.algorithm.listener.IterationStartsListener;
import jsprit.core.problem.VehicleRoutingProblem;
import jsprit.core.problem.solution.VehicleRoutingProblemSolution;
import jsprit.core.util.Resource;
import jsprit.core.util.Solutions;
import org.apache.commons.math.stat.descriptive.moment.StandardDeviation;
import org.apache.logging.log4j.LogManager;
import org.apache.logging.log4j.Logger;
import java.net.URL;
import java.util.Collection;
public class ExperimentalSchrimpfAcceptance implements SolutionAcceptor, IterationStartsListener, AlgorithmStartsListener{
final static Logger logger = LogManager.getLogger(ExperimentalSchrimpfAcceptance.class.getName());
private final double alpha;
private int nOfTotalIterations = 1000;
private int currentIteration = 0;
private double initialThreshold = 0.0;
private final int nOfRandomWalks;
private final int solutionMemory;
public ExperimentalSchrimpfAcceptance(int solutionMemory, double alpha, int nOfWarmupIterations) {
super();
this.alpha = alpha;
this.nOfRandomWalks = nOfWarmupIterations;
this.solutionMemory = solutionMemory;
logger.info("initialise " + this);
}
@Override
public boolean acceptSolution(Collection<VehicleRoutingProblemSolution> solutions, VehicleRoutingProblemSolution newSolution) {
boolean solutionAccepted = false;
if (solutions.size() < solutionMemory) {
solutions.add(newSolution);
solutionAccepted = true;
} else {
VehicleRoutingProblemSolution worst = null;
double threshold = getThreshold(currentIteration);
for(VehicleRoutingProblemSolution solutionInMemory : solutions){
if(worst == null) worst = solutionInMemory;
else if(solutionInMemory.getCost() > worst.getCost()) worst = solutionInMemory;
}
if(newSolution.getRoutes().size() < worst.getRoutes().size()){
solutions.remove(worst);
solutions.add(newSolution);
solutionAccepted = true;
}
else if(newSolution.getRoutes().size() == worst.getRoutes().size() && newSolution.getCost() < worst.getCost() + threshold){
solutions.remove(worst);
solutions.add(newSolution);
solutionAccepted = true;
}
}
return solutionAccepted;
}
@Override
public String toString() {
return "[name=schrimpfAcceptanceFunction][alpha="+alpha+"][warmup=" + nOfRandomWalks + "]";
}
private double getThreshold(int iteration) {
double scheduleVariable = (double) iteration / (double) nOfTotalIterations;
// logger.debug("iter="+iteration+" totalIter="+nOfTotalIterations+" scheduling="+scheduleVariable);
double currentThreshold = initialThreshold * Math.exp(-Math.log(2) * scheduleVariable / alpha);
return currentThreshold;
}
@Override
public void informAlgorithmStarts(VehicleRoutingProblem problem, VehicleRoutingAlgorithm algorithm, Collection<VehicleRoutingProblemSolution> solutions) {
reset();
logger.info("---------------------------------------------------------------------");
logger.info("prepare schrimpfAcceptanceFunction, i.e. determine initial threshold");
logger.info("start random-walk (see randomWalk.xml)");
double now = System.currentTimeMillis();
this.nOfTotalIterations = algorithm.getNuOfIterations();
/*
* randomWalk to determine standardDev
*/
final double[] results = new double[nOfRandomWalks];
URL resource = Resource.getAsURL("randomWalk.xml");
AlgorithmConfig algorithmConfig = new AlgorithmConfig();
new AlgorithmConfigXmlReader(algorithmConfig).read(resource);
VehicleRoutingAlgorithm vra = VehicleRoutingAlgorithms.createAlgorithm(problem, algorithmConfig);
vra.setNuOfIterations(nOfRandomWalks);
vra.getAlgorithmListeners().addListener(new IterationEndsListener() {
@Override
public void informIterationEnds(int iteration, VehicleRoutingProblem problem, Collection<VehicleRoutingProblemSolution> solutions) {
double result = Solutions.bestOf(solutions).getCost();
// logger.info("result="+result);
results[iteration-1] = result;
}
});
vra.searchSolutions();
StandardDeviation dev = new StandardDeviation();
double standardDeviation = dev.evaluate(results);
initialThreshold = standardDeviation / 2;
logger.info("warmup done");
logger.info("total time: " + ((System.currentTimeMillis()-now)/1000.0) + "s");
logger.info("initial threshold: " + initialThreshold);
logger.info("---------------------------------------------------------------------");
}
private void reset() {
currentIteration = 0;
}
@Override
public void informIterationStarts(int i, VehicleRoutingProblem problem, Collection<VehicleRoutingProblemSolution> solutions) {
currentIteration = i;
}
}