[petsc-users] How to use other matrix directly in petsc?

[Jed Brown]

On Thu, Nov 10, 2011 at 02:00, Bao Kai <paeanball at gmail.com> wrote:

> I guess the interface file is used to call the functions in umfpack to
> solve the linear system.  But the default matrix format in umfack should be
> csc, and I did get how the interface handle this problem.
>

So we give the CSR data structure to Umfpack which means that Umfpack sees
the transpose. Then we use the transpose-solve functionality.


> I go forward to try some linear solvers now.
>
> The matrix generated with my problem is a little poor, resulting from a
> mixed finite element method, asymmetric and indefinite. And the inclusion
> of irregular boundary makes it worse.  This is actually one reason I began
> with a direct solver.
>
> If you have any suggestions on solve this kinds of linear systems, please
> tell me.
>

Start with a direct solver. Once you have things working, you can change
the discretization of boundary conditions to be better conditioned and look
at iterative solvers (which are somewhat technical for indefinite problems).
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