I'm the author of the book... It may be fairly simple for you to change your design to generate a static call graph for the nodes using topographical sort. The

I'm the author of the book... It may be fairly simple for you to change your design to generate a static call graph for the nodes using topographical sort. Then on each "tick" you simply execute each node, in order, from top to bottom. I always like to use a stack to schedule execution because I can then change the algorithm that schedules them to use a very different method. - Matt Carkci