[petsc-users] Erro in solution

[Jed Brown]

On Mon, May 9, 2011 at 18:29, Danesh Daroui <danesh.daroui at ltu.se> wrote:

> No I didn't put "no-debugging" when I compiled. I will re-compile it. I
> am solving a set of Maxwell equations in integral form. I know that my
> coefficient matrix has a large condition number too. Would you please
> explain more about "-ksp_view" and "-log_summary"?
>

Just run your code with these options. They are put in a database by
PetscInitialize() and used by the solver when you called
KSPSetFromOptions().


> How can I use these
> options? I think the problem is deeper than some sort of compilation
> flags. Can I get number of iterations and know whether the solution has
> converged or not?
>

Yes, both in code and on the command line. Run with -help for full options
and references to the API. -ksp_monitor -ksp_converged_reason will be a good
start.


> In my case, the slow convergence can be due to badly
> conditioned matrices. I expected to use default preconditioner which
> should ILU I guess.
>

Yeah, -ksp_view will show the configuration for the solver. ILU may not work
well for your problem.
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