[petsc-users] How to specify a preconditioner matrix for pc_fieldsplit_type Schur?

[Thomas Witkowski]

Can some of you give me an example how to specify a preconditioner 
matrix in the case I have a fieldsplit preconditioner of Schur type? Or 
in the notation of the manual, how to set Sp in ksp(S, Sp) [see manual 
p. 87].

Thomas