I found there were few simple examples while trying to learn how to use the SUNDIALS libraries. Here are a few simple examples for those starting to utilize the SUNDIALS libraries.

Within src is an example using the CVODE library to solve a simple 2d ODE, treating it as a stiff system. The system is based off of boost's stiff system example at:

• https://www.boost.org/doc/libs/1_67_0/libs/numeric/odeint/doc/html/boost_numeric_odeint/tutorial/stiff_systems.html

for comparison purposes.

SUNDIALS is a SUite of Nonlinear and DIfferential/ALgebraic equation Solvers released by the Lawrence Livermore National Laboratory.

• https://computing.llnl.gov/projects/sundials

To download the libraries go to their software download page:

• https://computing.llnl.gov/projects/sundials/sundials-software

Libraries such as CVODE can be downloaded individually on the above page. There is also a link on that page to download the entire SUNDIALS library.

The online documentation gives a good tutorial for how to install the software depending on OS:

• https://sundials.readthedocs.io/en/latest/Install_link.html

*Note: The instructions above tell the user to change the generate settings for the install prefix to /usr/casc/sundials/instdir but for the GenericMakeFile it is more simple to leave the ccmake settings as is and keep the generate settings for the install prefix as the default option:

/usr/local

More examples for SUNDIALS libraries can be found in the more-sundials-examples folder.

• Simple rootfinding example.

• Example of how to implement user data for the system. Building block for implementing solver for complex systems.
• Example of how to setup a parallel environment (MPICH2) and utilize CVODE's integration with the MPI protocol(N_Vector_Parallel).

• Simple serial example with adjoint sensitivity analysis for stiff systems.