[petsc-users] Erro in solution

[Danesh Daroui]

Hi,

Yes this is more or less what I am using, however in addition to surface
I use volume integrals too for current distributions. Well, I know that
condition number should be decreased in general to improve the
convergence, but can you please let me know what preconditioner did you
use? I have not used Fast Multipole Method because of high
approximations specially in lower frequencies.

Regards,

D.


On Tue, 2011-05-10 at 01:38 +0200, Renzhengyong wrote:
> HI，
> I was working on solving Maxwell equations by surface integral
> approaches. If you are working on this, try to decrease the condition
> numbers of your integral operators so that it is reasonable to use
> GMRES solver in a limited number of iterations, which is a need for
> applying fast multipole method. 
> 
> 
> 
> 
> Zhengyong
> 
> Zhengyong Ren,
> Institute of Geophysics, 
> Department of Geoscience,
> ETH Zurich, CH8092,
> Zurich, Switzerland. 
> 
> On 2011-5-9, at 19:57, Jed Brown <jed at 59A2.org> wrote:
> 
> 
> 
> > On Mon, May 9, 2011 at 19:06, Danesh Daroui <danesh.daroui at ltu.se>
> > wrote:
> >         Thanks for the tip, but I already have two different version
> >         of my
> >         solver with PARDISO and MUMPS. Sparse Direct Solvers gave us
> >         a great
> >         contribution but I need to move to O(n^2) time complexity,
> >         So I really
> >         need to employ iterative solvers! :)
> > 
> > I'm confused. Is your problem dense? If so, then it doesn't make
> > sense to use sparse solvers. If it is sparse, then the asymptotics
> > for a direct solver are O(n^{3/2}) flops and O(n log n) space in two
> > dimensions and O(n^2) flops and O(n^{4/3}) spare in three
> > dimensions.
> > 
> > 
> > You can still use PETSc, but sparse preconditioners won't help you.
> > In particular, ILU is just a really crappy direct solver if you use
> > it on a dense matrix. Are there preconditioners for your problem in
> > the literature? Can it be done with a hierarchical method like FMM?
> 
>