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:
./configure --with-umfpack
make all
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):
SparseDirectUMFPACK solver;
solution = system_rhs;
solver.solve (system_matrix, solution);