Hey Sean, I've implemented a new Fitness which has almost the same methods like Koza-Fitness. But now ECJ is Breeding forever after the first evaluation. I'm using SizeFairCrossover BreedingPipeline and my Threaddump looks so: "Thread-11" prio=10 tid=0x00002aef202c7000 nid=0x3a5c runnable [0x00002aef26076000] java.lang.Thread.State: RUNNABLE at java.lang.Integer.hashCode(Integer.java:733) at java.util.HashMap.put(HashMap.java:372) at ec.gp.breed.SizeFairCrossoverPipeline.traverseTreeForDepth(SizeFairCrossoverPipeline.java:645) at ec.gp.breed.SizeFairCrossoverPipeline.produce(SizeFairCrossoverPipeline.java:330) at ec.breed.MultiBreedingPipeline.produce(MultiBreedingPipeline.java:135) at ec.simple.SimpleBreeder.breedPopChunk(SimpleBreeder.java:377) at ec.simple.SimpleBreederThread.run(SimpleBreeder.java:483) at java.lang.Thread.run(Thread.java:662) Locked ownable synchronizers: - None Does my fitness miss something crucial? Here's an abstract of my methods: setFitness(EvolutionState, float) //stores the fitness value and the generation in class variables fitness() isIdealFitness() equivalentTo(Fitness) betterThan(Fitness) fitnessToString() fitnessToStringForHumans() createdAt() //returns the generation when the fitness was created readFitness(EvolutionState, LineNumberReader) writeFitness(EvolutionState, DataOutput) readFitness(EvolutionState, DataInput) setToMeanOf(EvolutionState, Fitness[]) If I change my Fitness to Koza again, I don't have any problems. Greetings Bojan ----- Ursprüngliche Mail ----- Von: "Sean Luke" <[log in to unmask]> An: [log in to unmask] Gesendet: Freitag, 19. Juli 2013 15:19:43 Betreff: Re: Getting generation of best fitness On Jul 18, 2013, at 10:10 AM, Bojan Janisch wrote: > is there a way to get the generation of the individual which holds the best fitness? ECJ does not do this: you'll have to store the evaluation date of individuals yourself. Sean