Hello, I tried lately in my ecj experiments to migrate from ecj19 to ecj20, however I had problems. Namely the program in ecj19 is functioning with the given .params file. I have MultiPopCoevolutionaryEvaluator for co-evolution of two species (bits and floats). However when trying to run the same program with ecj20 with the almost same .params file there is a problem stating: "java.lang.ClassCastException: ec.vector.FloatVectorIndividual cannot be cast to ec.vector.BitVectorIndividual at main.SonicApp.MyFitness.evaluate(MyFitness.java:279) at ec.coevolve.MultiPopCoevolutionaryEvaluator.performCoevolutionaryEvaluation(MultiPopCoevolutionaryEvaluator.java:251) at ec.coevolve.MultiPopCoevolutionaryEvaluator.evaluatePopulation(MultiPopCoevolutionaryEvaluator.java:167) at ec.simple.SimpleEvolutionState.evolve(SimpleEvolutionState.java:76) at main.SonicApp.StartEvolExprThread.run(StartEvolExprThread.java:265) at main.SonicApp.StartEvolExprThread.run(StartEvolExprThread.java:200)" I said "almost same .params" since I am aware that there are some changes in ecj20, so the change in the .params file was minimal - only to remove the stuff that is not anymore supported in the new ecj20 version. Here is the part of the adapted .params file, supposed to run with ecj20: " eval.num-current = 4 eval.num-elites = 1 eval.num-prev = 2 eval.select-current = ec.select.RandomSelection eval.select-prev = ec.select.RandomSelection eval.subpop.0.select = ec.select.TournamentSelection eval.subpop.0.select.size = 2 #--- #-eval.subpop.0.num-elites = 1 #-eval.subpop.0.num-rand-ind = 5 #-eval.subpop.0.num-ind = 2 eval.subpop.1.select = ec.select.TournamentSelection eval.subpop.1.select.size = 2 #--- #-eval.subpop.1.num-elites = 1 #-eval.subpop.1.num-rand-ind = 5 #-eval.subpop.1.num-ind = 2 pop.subpops = 2 ... " Only the parts starting with "#-" have been commented out. Everything else is the same. The program in ecj19 runs. The program with ecj20 doesn't run. I guess that the problem can be probably tracked to the changes in the "MultiPopCoevolutionaryEvaluator.java" but I am not sure ?! Any comments/help on how to solve this issue ? ...By the way, I also didn't got reply on my previous questions in message with subject: "Setting up the genome size and other evolutionary parameters in the program code" :( Nikola