Matrix solvers?

[billy at dem.uminho.pt]

Hi,

I am using a single computer and several processes. I am using KSPGMRES for
solving matrices. When I use increase the number of processes I have problems
solving the matrix. Is there a more optimized solver for parallel processing?

When I update ghost cells information with VecGhostUpdateBegin/End() do I need
to call MPI_Barrier to assure that all ghost information is updated before
proceeding or is this already done by the VecGhostUpdateBegin/End()?

I have it almost working. Thanks for your help. 

Billy.