[petsc-users] problems using MUMPS as a linear solver

[Dominik Szczerba]

> This can happen if the linear system is very ill conditioned. You can run
> the direct solve inside -ksp_type richardson for a more classical "iterative
> refinement". Using a Krylov method is generally better. Because of the way
> GMRES preconditioning works, converging after one iteration still means two
> preconditioner applications (so much cheaper than factorization that you
> probably don't notice it). In contrast, one iteration of FGMRES only does
> one preconditioner application.

Yes, the system is badly conditioned. But am I right with my
(experimental) finding that the ultimate way to go is -ksp_type
preonly? Will it do what I want: just solve my system exactly once
using MUMPS and not Krylov?

Thanks
Dominik