ODE solver integrator options

The integrator used by the ODE solver of the CIF simulator, can be configured using several options.

Integration algorithm

The ODE solver integrator algorithm option (ODE solver: ODE integrator category) can be used to configure the integrator algorithm to use. The following algorithms are available:

The algorithms differ in the complexity of the systems of ODEs that they can handle, their performance, the precision of their results, etc. All these algorithms use an adaptive step size.

Absolute and relative tolerance

The ODE solver integrator absolute tolerance option (ODE solver: ODE integrator category) and the ODE solver integrator relative tolerance option (ODE solver: ODE integrator category), can be used to configure how precise the results of the integrator should be. The lower the tolerance (or error), the higher the precision of the results, but also the more computing time it costs to get to that precision. The absolute precision is the difference between the prediction and the actual value, while the relative precision is that same difference, as a fraction of the actual value. In the latter case, precision reduces with increasing values.

Minimum and maximum step size

The interval between two consecutive time points calculated by the integrator can be configured using the ODE solver integrator minimum step size option (ODE solver: ODE integrator category) and the ODE solver integrator maximum step size option (ODE solver: ODE integrator category).

The default minimum step size is 1e-15 and the default maximum step size is 0.5. Note however that the last step can be smaller than the value specified for the minimum step size option.

Increasing the maximum default step size may lead to better performance, but can also lead to less precision, and root finding problems.

Number of steps

The ODE solver integrator number of steps option (ODE solver: ODE integrator category) can be used to configure the number of steps to use for the experimental Adams-Bashforth and Adams-Moulton integrators. The number of steps must be greater or equal to two.