using MUMPS with mg

[Barry Smith]

On Jun 23, 2008, at 4:52 AM, Thomas Geenen wrote:

> dear Petsc users,
>
> when using mg with Petsc (ml to be precise)
> the default solver on the coarsest level is "redundant"
> (I could not find much info in either the usermanual or de online
> manuals about this solver)
>
> it seems to be a sequential LU factorization running on all cpu's at
> the same time?
> doing the same thing?

    Correct.
>
>
> i try to use MUMPS instead.
> i try to invoke mumps by calling
> ierr = PetscOptionsSetValue("-mg_coarse_ksp_type", "preonly");
> ierr = PetscOptionsSetValue("-mg_coarse_mat_type", "aijmumps");
> ierr = PetscOptionsSetValue("-mg_coarse_pc_type", "lu");
>
> this gives me
>
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: No support for this operation for this object type!
> [0]PETSC ERROR: Matrix type mpiaij  symbolic
>
> so apparently Petsc did not convert the matrix on the coarsest level.
> if i remove the pc_type the conversion option is ignored and Petsc
> uses redundant.

   How are you generating the coarse grid matrix? Do you get it with  
DAGetMatrix()?
Or MatCreateMPIAIJ()? Do you set the matrix prefix to -mg_coarse?
It is not set automatically. You need to either call MatSetFromOptions()
on the coarse matrix or directly call MatSetType() with aijmumps to set
it the type.

    Barry






>
>
>
>
> cheers
> Thomas
>