Hi, I'm monitoring a strange behavior of MASON using the same simulation with and without a GUI. I'm creating my non gui simulation by using public Trophic01Sim(long seed) { super(new MersenneTwisterFast(seed), new ScheduleExtended()); } Setting seed to 1 will cause an exhausted simulation (no events because all my agents died) after 214 steps. Invoking the same simulation with a gui by using public Trophic01SimWithUI() { this(new Trophic01Sim(1)); } will lead to a different result (my simulation reaches some sort of equilibrium and won't stop). Even changing the non gui constructor to public Trophic01Sim(long seed) { super(new MersenneTwisterFast(1), new ScheduleExtended()); } has no effect. I get the same result for the non gui version after 214 steps but with the gui I get an equilibrium. I don't use or manipulate MersenneTwisterFast but it is used by the Schedule class for shuffling the events at the same time step. Is there (an intended) different behavior between gui and non gui simulations? For me it is a disturbing feature/bug because I'd like to do some simulation runs without the gui (much faster) and run the interesting ones with a gui for visualization (but getting different results). Please help, Jörg