[petsc-dev] Preconditioner for Schur complement (pcfieldsplit)

[Thomas Witkowski]

Jed Brown wrote:
> On Tue, Mar 29, 2011 at 12:55, Thomas Witkowski 
> <thomas.witkowski at tu-dresden.de 
> <mailto:thomas.witkowski at tu-dresden.de>> wrote:
>
>     I have implemented a Schur complement solver based on the
>     fieldsplit preconditioner, i.e., my code is executed with the
>     option -pc_fieldsplit_type schur. How can I define a
>     preconditioner Sp for the inner Schur complement solution? I want
>     to define the preconditioner in an explicit way, thus build a
>     matrix that should approximate S in some way!
>
>
> See PCFieldSplitSchurPrecondition and (perhaps) PCShell. Perhaps if 
> you give a more specific example, we can give more specific suggestions.
PCFieldsplitSchurPrecondition seems to do what I want. But how to create 
the matrix for the preconditioner? I'm a little bit confused about it 
because the matrix/operator S acts on an index range that does not start 
from 0 and is not continuous, because each rank owns only some parts of 
the interior domain boundaries.

Thomas