There are three basic solution techniques, or controllers: Simulation, Optimization, and Rulebased Simulation, Rulebased Simulation and Optimization both require the construction of a Simulation model; therefore, all models need a basic simulation component. For this reason, the Simulation controller is the default selection when the Run Control dialog is first opened. Select a different controller from the menu to view the other controller choices.

A large number of slots are associated with each controller. When an object is created, it is initialized with the slots belonging to the selected controller. When a new controller is selected after the objects have been constructed, the original slots remain in memory and new slots are allocated for the new controller. This situation may leave many unnecessary slots which affect memory and model size. When building the initial simulation model, the Simulation controller must be selected.