## Example 12

The grid layout is the same as ex1, but with nodal unknowns. The solver is PCG preconditioned with either PFMG or BoomerAMG, selected on the command line.

We recommend viewing the Struct examples before viewing this and the other SStruct examples. This is one of the simplest SStruct examples, used primarily to demonstrate how to set up non-cell-centered problems, and to demonstrate how easy it is to switch between structured solvers (PFMG) and solvers designed for more general settings (AMG).