Currently only an interface to the Runge-Kutta methods: [ARKode](https://computation.llnl.gov/projects/sundials/arkode) The interface is almost certainly going to change. Sundials gives a rich set of "combinators" for controlling the solution of your problem and reporting on how it performed. The idea is to initially mimic hmatrix-gsl and add extra, richer functions but ultimately upgrade the whole interface both for sundials and for gsl.