package de.mh4j.examples.solver;
import org.slf4j.LoggerFactory;
import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import de.mh4j.examples.ExampleSolverStateListener;
import de.mh4j.examples.Sorting;
import de.mh4j.solver.Solver;
import de.mh4j.solver.simulatedAnnealing.AbstractLocalSearchSolver;
public class LocalSearchSorter extends AbstractLocalSearchSolver<Sorting> {
private final int amountOfNumbers;
public LocalSearchSorter(int amountOfNumbers) {
this.amountOfNumbers = amountOfNumbers;
}
/**
* Creates an initial random sorting.
*/
@Override
protected Sorting createInitialSolution() {
return Sorting.createRandomSorting(amountOfNumbers);
}
/**
* A random neighbor is created by choosing two unequal random indices in
* the sorting array and swapping the numbers at this position.<br>
* Hopefully one of the swapped numbers will be nearer to its optimal
* position in the sorting and decrease the cost of the whole new sorting.
*/
@Override
protected Sorting createRandomNeighbor() {
Sorting neighbor = new Sorting(currentSolution);
int randomIndex1 = randomizer.nextInt(currentSolution.getAmountOfNumbers());
int randomIndex2 = randomizer.nextInt(currentSolution.getAmountOfNumbers() - 1);
if (randomIndex1 <= randomIndex2) {
randomIndex2++;
}
neighbor.swapIndices(randomIndex1, randomIndex2);
return neighbor;
}
/**
* Checks if we have found the optimal solution with costs zero or if the
* number of steps the algorithm has been running has exceeded the maximum
* number of steps.<br>
* <br>
* <b>Note:</b> This termination condition is some arbitrarily chosen
* example. Real termination conditions will have to be founded in some
* serious considerations.
*/
@Override
public boolean hasFinished() {
if (currentSolution.getCosts() == 0) {
return true;
}
else {
return getNumberOfSteps() >= 100000;
}
}
public static void main(String[] args) throws InterruptedException {
Logger log = (Logger) LoggerFactory.getLogger(LocalSearchSorter.class);
log.setLevel(Level.WARN);
Solver<Sorting> solver = new LocalSearchSorter(100);
solver.addStateListener(new ExampleSolverStateListener<Sorting>());
Thread solverThread = new Thread(solver);
solverThread.start();
}
}