On Sun, Oct 28, 2012 at 9:38 AM, w_ang_temp <w_ang_temp at 163.com> wrote:
> Hello, Jed > Thanks for your timely reply. I deal with the soil-water coupled > problem in geotechnical engineering, > whose stiffness matrix is ill-conditioned. I have did some work about it, > mainly finding the effective > solvers and preconditioners. I used the command line option like this: > mpiexec -n 4 ./ex4f -ksp_type cgs -pc_type sor -ksp_rtol 1.0e-15 > -ksp_converged_reason. > If SOR works as a preconditioner, then definitely use AMG as Jed suggested. It is almost certain to work. Matt > So, I also want to use the multigrid just like the simple command. > There is only a little introduction > about multigrid in the manual. Multigrid is complex and not a easy thing > for me, so I just need to konw how > to use it simply in PETSc to solve the Ax=b system. > Thanks. > Jim > > > > > > >At 2012-10-28 21:17:00,"Jed Brown" <jedbrown at mcs.anl.gov> wrote: > > >Algebraic multigrid can be used directly, -pc_type gamg > -pc_gamg_agg_nsmooths 1. Geometric either required that you use the PCMG > interface to set >interpolation (and provide a coarse operator for > non-Galerkin) or use a DM that provides coarsening capability. > > >What kind of problem are you solving? > >>On Oct 28, 2012 6:09 AM, "w_ang_temp" <w_ang_temp at 163.com> wrote: > >> >>Hello, >> >> I want to use the multigrid as a preconditioner. The introduction >> about it in the manual is little. >> >>So are there some typical examples or details about multigrid? Is it >> used just like other preconditioners >> >>like jacobi, sor, which can be simply used in the cammand line options? >> >> Thanks. >> >> >> Jim >> >> >> > > -- 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20121028/efc91abf/attachment.html>
