Standard solver vs fixed-step solver

Solvers: standard and fixed-step It is important to note that discontinuity handling is active only when using standard solver.

Unlike a variable step solver, a fixed step solver cannot reduce its integration step size, and come back to a time at which a discontinuity has occurred. Moreover, a fixed step solver does not perform any convergence tests and will not be perturbed by a sharp change in the derivative values of state variables. A fixed step solver simply relies on the integration step specified by the user and sticks to this value throughout the simulation.

As the submodel code remains the same for both types of solver, fixed step solvers provided in Simcenter Amesim disable the discontinuity handling mechanism. This means that equations C1 or C2 will be directly used, depending on the current value of x, as in the pseudo code described in chapter 3. From a technical point of view, the submodel calculation functions are always called with "flag==0". This implies that the state of the submodel, stored in ic[] array item, will be up to date at every call to the submodel.