Hello Matt, I am not sure I understand your point. I guess you mean that inside petsc only a version of Gmres working with preconditioning is not yet implemanted , Am I right ?
Tahar Le 22 avr. 2013 ? 14:12, Matthew Knepley a ?crit : > On Mon, 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. > > Krylov methods do not work with preconditioners. You have a Poisson problem, > so as abundantly documented in the literature, you should use multigrid. The > easiest thing to try is > > -pc_type gamg -pc_gamg_agg_nsmooths 1 > > Thanks, > > Matt > > 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. > > > > -- > What most experimenters take for granted before they begin their experiments > is infinitely more interesting than any results to which their experiments > lead. > -- Norbert Wiener -------------------------------------------- T. Amari Centre de Physique Theorique Ecole Polytechnique 91128 Palaiseau Cedex France tel : 33 1 69 33 42 52 fax: 33 1 69 33 49 49 email: <mailto:tahar.amari at polytechnique.edu> URL : http://www.cpht.polytechnique.fr/cpht/amari -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20130422/b8de262e/attachment.html>
