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6.3) Numerical Integration: Accuracy And Stability


Numerical integration is never perfectly accurate and error free. The accuracy of a solution depends on the size of the time-steps we use, and this can be set in Vensim. Using smaller time-steps means we need more of them to cover the time interval we want to simulate. There is always a trade-off between accuracy and speed.

As well as accuracy, the stability of solutions is a consideration. Whereas the accuracy of a simulations tells us how close to the real solution our simulation remains, stability tells us whether it stays near the solution at all. The figure below indicates what happens in an unstable simulation of exponential decay.