java.lang.IllegalArgumentException: Comparison method violates its general contract

[DKorosec]

Exception in thread "main" java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at java.util.TimSort.mergeHi(Unknown Source)
	at java.util.TimSort.mergeAt(Unknown Source)
	at java.util.TimSort.mergeForceCollapse(Unknown Source)
	at java.util.TimSort.sort(Unknown Source)
	at java.util.Arrays.sort(Unknown Source)
	at java.util.ArrayList.sort(Unknown Source)
	at java.util.Collections.sort(Unknown Source)
	at org.um.feri.ears.benchmark.RatingBenchmark.setWinLoseFromResultList(RatingBenchmark.java:161)
	at org.um.feri.ears.benchmark.RatingBenchmark.run(RatingBenchmark.java:219)
	at MainBenchMarkTest.TEST_ALGO(MainBenchMarkTest.java:53)
	at MainBenchMarkTest.main(MainBenchMarkTest.java:88)

When running the following configuration I get this exception printed above. (It takes some time, but it will be 100% reproducible)

TEST_ALGO(5, 10, 70, 75, 1508185232848L, 2);

public static void TEST_ALGO(int from_f, int to_f, int from_c, int to_c, long seed, int repeat)
	{
		System.out.println("seed: "+seed);
		Util.rnd.setSeed(seed);

		ArrayList<Algorithm> players = new ArrayList<Algorithm>();
		players.add(new DEE007(10,0.7,0.89,"CrepA"));
		players.add(new DEE007(10,0.71,0.79,"CrepB"));
		if(true)
		{
			for(int pop = 10; pop <= 100; pop += 10)
			{
				for(int c = from_c; c <= to_c; c+=1)
				{
					for(int f = from_f; f <= to_f; f+=1)
					{
						double cParam = c/100.0d;
						double fParam = f/100.0d;
						if(cParam > 1)
							cParam = 1;
						if(fParam > 1)
							fParam = 1;
						String aname = "{{"+Integer.toString(pop)+","+Double.toString(cParam)+","+Double.toString(fParam)+"}}";
					    Algorithm algorithm = new DEE007(pop, cParam, fParam, "new_Dominik"+aname);
					    players.add(algorithm);
					}
				}
			}
		}
		ResultArena ra = new ResultArena(100);
		RatingRPUOed2 suopm = new RatingRPUOed2(); //Create banchmark
		suopm.setDisplayRatingIntervalChart(false);
		for (Algorithm al:players) {
		    ra.addPlayer(al.getID(), 1500, 350, 0.06,0,0,0); //init rating 1500
		    suopm.registerAlgorithm(al);
		}
		BankOfResults ba = new BankOfResults();
		suopm.run(ra, ba, repeat); 
		ArrayList<Player> list = ra.recalcRatings();
		//for(int i=0;i < 10 && i < list.size();i++) {
			System.out.println(list.get(0)); //print rangs
		//}
	}

import java.util.ArrayList;

import org.um.feri.ears.algorithms.Algorithm;
import org.um.feri.ears.algorithms.AlgorithmInfo;
import org.um.feri.ears.algorithms.Author;
import org.um.feri.ears.problems.DoubleSolution;
import org.um.feri.ears.problems.StopCriteriaException;
import org.um.feri.ears.problems.Task;
import org.um.feri.ears.util.Util;

public class DEE007 extends Algorithm {
    int pop_size;
    double CR, F;
	ArrayList<DoubleSolution> pop;
	DoubleSolution best;
	//Initialize all agents {\displaystyle \mathbf {x} } \mathbf {x}  with random positions in the search-space.
	public DEE007(int ps, double CR, double F, String s) {
		pop_size = ps;
		this.CR = CR;
		this.F = F;
		ai = new AlgorithmInfo("","",s,s);  //EARS add algorithm name
		au =  new Author("E007", "N/A"); //EARS author info

	}
	public void init(Task taskProblem) throws StopCriteriaException {
		pop = new ArrayList<>();
		DoubleSolution tmp;
		for (int i=0; i<pop_size;i++) {
			if (taskProblem.isStopCriteria()) break;
			tmp = taskProblem.getRandomSolution();
			if (i==0) best = tmp;
			else if (taskProblem.isFirstBetter(tmp, best)) best = tmp;
			pop.add(tmp);
		}
	   	
	}
	
	@Override
	public DoubleSolution execute(Task taskProblem) throws StopCriteriaException {
		init(taskProblem);
		int a, b, c, R;
		DoubleSolution yEval;
		while (!taskProblem.isStopCriteria()) {
			for (int i=0; i<pop_size;i++) {
				if (taskProblem.isStopCriteria()) break;
				do 
				  a = Util.rnd.nextInt(pop_size);
				while (a==i);
				do 
					  b = Util.rnd.nextInt(pop_size);
				while ((b==i)||(b==a));
				do 
					  c = Util.rnd.nextInt(pop_size);
				while ((c==i)||(c==a)||(c==b));
				R = Util.rnd.nextInt(taskProblem.getNumberOfDimensions());
				double y[] = new double[taskProblem.getNumberOfDimensions()];
				for (int j=0; j<taskProblem.getNumberOfDimensions(); j++) {
					if ((Util.nextDouble()<CR) || (j==R)) {
						y[j] = taskProblem.setFeasible(pop.get(a).getDoubleVariables()[j]+F*(pop.get(b).getDoubleVariables()[j]-pop.get(c).getDoubleVariables()[j]),j);
					} else y[j] = pop.get(i).getDoubleVariables()[j];
				}
				yEval = taskProblem.eval(y);
				if (taskProblem.isFirstBetter(yEval, pop.get(i))){
					pop.set(i, yEval);
					if (taskProblem.isFirstBetter(yEval, best)) best = yEval;
				}
			}
		}
		return best;
	}

	@Override
	public void resetDefaultsBeforNewRun() {
		// TODO Auto-generated method stub
		
	}

}

[Ravby]

The fitness comparator has been fixed and simplified. 068dbad