[petsc-users] Trying to set up a field-split preconditioner

[Matthew Knepley]

On Fri, Jul 19, 2013 at 7:56 PM, subramanya sadasiva <potaman at outlook.com>wrote:

>  Hi,
> I am trying to set up a fieldsplit preconditioner for my Cahn Hilliard
> solver and I get the following error,
>

You have to tell the PCFIELDSPLIT about the dofs in each field. So

1) You are probably not using a DA, since it would tell it automatically

2) If you have a saddle point, you can use
-pc_fieldsplit_detect_saddle_point

3) If none of those apply, you can set a PetscSection describing your
layout to the DM for the solver.
     Since this is new, I suspect you will need help, so mail back.

  Thanks,

     Matt


>
> [0]PETSC ERROR: --------------------- Error Message
> ------------------------------------
> [0]PETSC ERROR: Petsc has generated inconsistent data!
> [0]PETSC ERROR: Unhandled case, must have at least two fields, not 0!
> [0]PETSC ERROR:
> ------------------------------------------------------------------------
>
> These are the options that I am using,
> -ch_solve is just a prefix.
>
>
>
> -ch_solve_pc_type fieldsplit
> -ch_solve_pc_fieldsplit_type schur
> -ch_solve_fieldsplit_block_size 2
> -ch_solve_fieldsplit_0_field 1
> -ch_solve_fieldsplit_1_field 0
> -ch_solve_fieldsplit_0_ksp_type cg
> -ch_solve_fieldsplit_0_pc_type hypre
> -ch_solve_fieldsplit_0_pc_type_hypre boomeramg
> -ch_solve_fieldsplit_1_ksp_type cg
> -ch_solve_fieldsplit_1_pc_type hypre
> -ch_solve_fieldsplit_1_pc_type_hypre boomeramg
>
> Any ideas?
>
> Thanks,
> Subramanya
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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