So it look alike your operator is not symmetric but is a scalar Laplacian with constant coefficients (?)
You should using AMG. '-pc_type hypre' if you are configured with hypre and '-pc_type gamg' if not. On Apr 22, 2013, at 7:56 AM, David Scott <d.scott at ed.ac.uk> wrote: > Hello, > > I am working on a fluid-mechanical code to solve the two-phase Navier?Stokes > equations with levelset interface capturing. I have been asked to replace the > pressure calculation which uses the SOR and Jacobi iterative schemes with a > Krylov subspace method. I have done this and the code is working but as I > have never used PETSc before I would like to know if improvements to my code, > or the run time parameters that I am using, could be made. > > I am using GMRES with a Block Jacobi pre-conditioner. I have tried Conjugate > Gradient with a Block Jacobi pre-conditioner but it diverges. If I use GMRES > for the first few thousand time steps and then swap to CG it does converge > but the speed of execution is somewhat reduced. > > I have attached relevant excerpts from the code. > > Yours sincerely, > > David Scott > -- > Dr. D. M. Scott > Applications Consultant > Edinburgh Parallel Computing Centre > Tel. 0131 650 5921 > > The University of Edinburgh is a charitable body, registered in > Scotland, with registration number SC005336. > <main_ns_hybrid_trimmed.F90><pressure_solver_trimmed.F90>
