Thanks. I will have a try.
Jim
? 2012-10-28 21:46:23?"Matthew Knepley" <knepley at gmail.com> ???
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
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