Discuss other iterative linear solvers + preconditioners and UMFPACK.
The UMFPACK solver is distributed with deal.II, but for license reasons, we do not enable it by default. If you want to use it, you have to do the following steps:
This builds the UMFPACK solver and adds support for it in the library. After that, you will be able to use the solver in the simplest possible way (note that the solver overwrites the right hand side vector with the solution, so only one vector has to be passed to it):
./configure --with-umfpack make all
SparseDirectUMFPACK solver; solution = system_rhs; solver.solve (system_matrix, solution);