[petsc-dev] FieldSplit and PCLSC

[domenico.borzacchiello at univ-st-etienne.fr]

Hi,
I'm solving Stokes equations with Pc FieldSplit and Schur Complement
Preconditioning. If I use a direct solver for the block A(0,0) and no
preconditioning for the Schur Complement (just fgmres), the outer solver
converges in typically 1-2 iterations and the inner solver for Schur
Complement in 10-15 iterations depending on the problem size. If I try to
precondition the Schur Complement with PCLSC (dev version) with direct
solution for the product A(2,1)*A(1,2) the Schur Complement solver takes
350+ iterations to converge. What could be the cause of this behavior?
I've used LSC before (not in PETSC however) for transient Navier-Stokes
and it used to work fine.
Thanks
Domenico