The most common causes of slow running models are:
- The number of equations being solved is large (greater than 15).
- A phase in the model completely disappears (e.g. a solid phase dissolves completely) during the simulation. Very small volume phases can occasionally cause numerical problems within the solvers that cause a large number of steps to be taken.
- A discontinuity is present in the model solution caused by a calculate statement (e.g. ‘If’ statements used to implement a process control action)
- Rapid changes in profiled variables. A sudden change (a discontinuity) will force the solver to take small steps to capture the change accurately.
- The number of data points in the model is large (greater than 100). The solver will stop and report a value at times corresponding to each data point. This means that the more data points you have, the slower the run will be.
- Wrong choice of solver. Another solver may run the model more quickly.
- Model parameter inconsistencies (e.g. rate constants or concentrations are orders of magnitude too high). Check the model in the simulator windows.
- Other model inconsistencies (e.g. imposing pressure in a set volume gas phase).
Troubleshoot models that run slowly.