13. Stepper Data Structure

This section presents the SUNStepper base class which represents a generic solution procedure for IVPs of the form

(13.1)\[\dot{v}(t) = f(t, v) + r(t), \qquad v(t_0) = v_0,\]

on an interval \(t \in [t_0, t_f]\). The time dependent forcing term, \(r_i(t)\), is given by

(13.2)\[r(t) = \sum_{k = 0}^{n_{\text{forcing}}-1} \left( \frac{t - t_{\text{shift}}}{t_{\text{scale}}} \right)^{k} \widehat{f}_k.\]

SUNStepper provides an abstraction over SUNDIALS integrators, custom integrators, exact solution procedures, or other approaches for solving (13.1). These are used, for example, in operator splitting and forcing methods to solve inner IVPs in a flexible way.