SUNDIALS is an award-winning SUite of Nonlinear and
DIfferential/ALgebraic equation Solvers implemented with the goal of
providing robust time integrators and nonlinear solvers that can
easily be incorporated into existing simulation codes. The primary
design goals are to require minimal information from the user, allow
users to easily supply their own data structures underneath the
packages, and allow for easy incorporation of user-supplied linear
solvers and preconditioners. The main numerical operations performed
in these codes are operations on data vectors, and the codes have been
written in terms of interfaces to these vector operations. The codes
also come with default vector structures with pre-defined operation
implementations for serial, shared-memory parallel (openMP and
PThreads), and distributed memory parallel (MPI) environments in case
a user prefers not to supply their own structures. In addition, all
parallelism is contained within specific vector operations (norms, dot
products, etc.). No other operations within the solvers require
knowledge of parallelism.