Hello everybody, I have a question concerning the fitness evaluation (in coevolution). I want to do worst case optimization and I am testing my solutions (population 1) against scenarios (population 2). The fitness of my solutions is quite easy to determine - it's the worst outcome of the interactions and I can more or less use SimpleFitness. The fitness of the scenarios is more difficult to determine - which is why I would like to test a few ideas before deciding on one. Therefore I need to define a new fitness and I am wondering where to start. The fitness of one scenario depends not only on the outcome of the interactions with the solutions but also on the performance of the other scenarios. For example: Imagine each solution is tested against each scenario and then lists the scenarios according to the results. The worst case scenario for example would get the highest rank. Now the fitness of a scenario is equal to the highest rank it achieves for any rule. You see, I need quite a lot of information and before I started using ECJ I imagined I would first do all the interactions, get a matrix of the results, and then compute the fitness values. Now I found out that in ECJ the fitness is actually computed during the interaction of two individuals. Where in the algorithm do I have access to the information I need and can define the fitness accordingly? As it seems to me, I cannot do it just by modifying Fitness. Thanks for every comment! Johanna