public TourConfigurationCollection calculate(
ProblemData problemData, TourConfigurationCollection tourConfigurationCollection) {
TourConfiguration configuration = tourConfigurationCollection.getFittest();
// 2-opt
int numberOfNodesEligibleToBeSwapped = problemData.getProblemSize();
int numberOfSwaps = 0;
start_again:
while (true) {
if (numberOfSwaps > 10000) {
break;
}
double best_distance = configuration.calculateTourLength();
for (int i = 0; i < numberOfNodesEligibleToBeSwapped - 1; i++) {
for (int k = i + 1; k < numberOfNodesEligibleToBeSwapped; k++) {
TourConfiguration new_route = optSwap(configuration, i, k);
double new_distance = new_route.calculateTourLength();
if (new_distance < best_distance) {
configuration = new_route;
numberOfSwaps++;
if (notify(configuration)) {
return tourConfigurationCollection;
}
continue start_again;
}
}
}
break;
}
return tourConfigurationCollection;
}
protected TourConfiguration optSwap(TourConfiguration configuration, int i, int k) {
TourConfiguration new_route = TourConfiguration.create(configuration);
// 1. take route[0] to route[i-1] and add them in order to new_route
for (int j = 0; j < i; j++) {
new_route.setStep(j, configuration.get(j));
}
// 2. take route[i] to route[k] and add them in reverse order to
// new_route
for (int j = i; j <= k; j++) {
new_route.setStep(j, configuration.get(k - (j - i)));
}
// 3. take route[k+1] to end and add them in order to new_route
for (int j = k + 1; j < configuration.getSize(); j++) {
new_route.setStep(j, configuration.get(j));
}
return new_route;
}