What is the best solver a poisson type eqn.

[Lisandro Dalcin]

On Fri, Jun 12, 2009 at 11:13 AM, Christian
Klettner<christian.klettner at ucl.ac.uk> wrote:
> Sorry that I sent this twice. No subject in the first one.
>
> Dear PETSc Team,
> I am writing a CFD finite element code in C. From the discretization of
> the governing equations I have to solve a Poisson type equation which is
> really killing my performance. Which solver/preconditioner from PETSc or
> any external packages would you recommend? The size of my problem is from
> ~30000-100000 DOF per core. What kind of performance would I be able to
> expect with this solver/preconditioner?

I would suggest KSPCG. As preconditioner I would use ML or
HYPRE/BoomerAMG (both are external packages)

> I am using a 2*quad core 2.3 GHz Opteron. I have decomposed the domain
> with Parmetis. The mesh is unstructured.
> Also, I am writing a code which studies free surface phenomena so the mesh
> is continually changing. Does this matter when choosing a
> solver/preconditioner? My left hand side matrix (A in Ax=b) does not
> change in time.

ML has a faster setup that BoomerAMG, but the convergence is a bit
slower. If your A matrix do not change, then likely BoomerAMG will be
better for you. In any case, you can try both: just build PETSc with
both packages, then you can change the preconditioner by just passing
a command line option.

>
> Best regards and thank you in advance,
> Christian Klettner
>

Disclaimer: the convergence of multigrid preconditioners depends a lot
on your actual problem. What I've suggested is just my limited
experience in a few problems I've run solving electric potentials.


-- 
Lisandro Dalcín
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