public void step(SimState state) {
    diffusers.step(state);

    // copy HeatBugs.this.valgrid2 to HeatBugs.this.valgrid
    HeatBugs heatbugs = (HeatBugs) state;
    heatbugs.valgrid.setTo(heatbugs.valgrid2);
  }
 /**
  * We'll have HeatBugs call this in its stop() method to give US a chance to call cleanup on our
  * underlying ParallelSequence so we don't leak threads.
  */
 public void cleanup() {
   diffusers.cleanup();
 }