[petsc-users] chelosky vs multigrid

[Fazlul Huq]

Thanks.

I have tried with large problem also (10^7 X 10^7). Even then I got
cholesky faster than multigrid.
But, the problem is 1D. May be that's the reason.

Thanks.
Sincerely,
Huq

On Mon, Dec 3, 2018 at 9:43 PM Jed Brown <jed at jedbrown.org> wrote:

> Fazlul Huq via petsc-users <petsc-users at mcs.anl.gov> writes:
>
> > Hello PETSc Developers,
> >
> > I am trying to solve a poisson equation using "-pc_type cholesky" and
> > "-pc_type hypre -pc_hypre_type boomeramg" and I got that cholesky
> > decomposition method takes
> > less time then multigrid method.
> > Is this expected?
>
> For small problems, yes.  If using Cholesky in practice, you may want to
> install SuiteSparse or MUMPS and use -pc_factor_mat_solver_type cholmod
> (or mumps).
>
> > I thought that multigrid method solve faster than cholesky
> > decomposition method.
>
> For sufficiently large problems (especially in 3D), yes.
>


-- 

Fazlul Huq
Graduate Research Assistant
Department of Nuclear, Plasma & Radiological Engineering (NPRE)
University of Illinois at Urbana-Champaign (UIUC)
E-mail: huq2090 at gmail.com
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