@Override
public void informAlgorithmStarts(
VehicleRoutingProblem problem,
VehicleRoutingAlgorithm algorithm,
Collection<VehicleRoutingProblemSolution> solutions) {
logger.info("prepare schrimpfAcceptanceFunction, i.e. determine initial threshold");
double now = System.currentTimeMillis();
/*
* 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.setMaxIterations(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);
double initialThreshold = standardDeviation / 2;
schrimpfAcceptance.setInitialThreshold(initialThreshold);
logger.info("took " + ((System.currentTimeMillis() - now) / 1000.0) + " seconds");
logger.debug("initial threshold: " + initialThreshold);
logger.info("---------------------------------------------------------------------");
}
