Purpose of Thorn

Thorn EllBase provides the basic functionality for

• registering a class of elliptic equations
• register a solver for any particular class

The solvers are called by the user through a unique interface, which calls the required elliptic solver for a class using the name under which the solver routine is registered.

EllBase itself defines the elliptic classes

1. flat: Ell_LinFlat
   solves a linear elliptic equation in flat space: $\nabla \phi + M \phi +N = 0$

2. metric: Ell_LinMetric
   solves a linear elliptic equation for a given metric: $\nabla_{g} \phi + M \phi + N = 0$
3. conformal metric: Ell_LinConfMetric
   solves a linear elliptic equation for a given metric and a conformal factor: $\nabla_{cg} \phi + M \phi + N = 0$
4. generic: solves a linear elliptic equation by passing the stencil functions. There is support for a maximum of 27 stencil functions ($3^3$). This is not implemented, yet.