This is a git repository for the code for a group of numerical integrators for time-dependent differential equations. They include the backward (implicit) Euler method, Spectral Deferred Corrections (SDC) method, and a Jacobian-Free Newton Krylov (JFNK) method** designed to acclearate the convergence of SDC for stiff systems.
A mathematical description/ theory behind the numerical integrators are in a .pdf file called math_nodes.pdf. I suggest reading that if you are interested in understanding the mechanics behind the algorithms.
Code documentation/users-guide for the JFNK may be found in the following document: users_guide.pdf