GPS-X Technical Reference

Miscellaneous 432
Simulation speed depends strongly on the values of the derivatives of the state
variables. You can reduce the absolute value of the lower and upper bounds on
the derivatives to speed up the simulation of discontinuities by eliminating sharp
peaks. These bounds can be found in the
General Data > System > Parameters > Numerical form. The best values to use
depend on the system in question. Try plotting the DO derivative (found in the
Process Data menu for each object), because this is the most sensitive state
variable in most cases. Get the maximum value during the run and then select the
bounds to be 50 percent of the highest value. Changing the bounds from the
default values (-1.e33 and 1.e33) can restrict the accuracy of the integration.
Sudden start-up or switching off of pumps (influent or other) can cause
discontinuities in the derivatives, and as a consequence, a delay in the processing
of the simulation. To prevent this, a smooth pump option is provided in the
General Data > System > Parameters > Numerical form, which starts and stops
pumps smoothly. This is strictly intended as a numerical feature and does not try
to simulate real pump discharges during transient periods. By default, the
smoothing is not used. If you experience problems when pumps are turned off or
on, try using smoothing.
Check the Log window for any messages printed during the run.
GPS-X Technical Reference