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
