[petsc-users] FW: [Fwd: Re: Question on asm]

[Matthew Knepley]

On Tue, May 14, 2013 at 2:35 PM, Isik Ali Ozcer
<isik.ozcer at mail.mcgill.ca>wrote:

> Hi All,
>
> Regarding ILU convergence at subdomain boundaries, I need to add to my
> colleague's message that we followed a very basic tutorial that shows
> matrix and rhs assembly, preconditioner and solver setup, and finally a
> KSPsolve.  We did not prepare any application ordering information or index
> sets. I am not sure if Petsc in our implementation has all the info it
> needs to perform proper overlapping operations with ASM. Do we need to
> worry about setting up AO and IS contexts before attempting KSPsolve with
> ASM and ILU?
>

No the matrix is enough.

   Matt


> Thanks a lot and have a great day,
>
> Isik
> petsc-newb
>
>
>
> -------- Original Message --------
> Subject:        Re: [petsc-users] Question on asm
> Date:   Tue, 14 May 2013 13:03:38 -0500
> From:   Jed Brown <jedbrown at mcs.anl.gov>
> To:     Konstantinos Kontzialis <ckontzialis at lycos.com>,
> petsc-users at mcs.anl.gov
>
>
>
> Konstantinos Kontzialis <ckontzialis at lycos.com> writes:
>
> > Dear all,
> >
> > I am using asm as a preconditioner for solving the Navier Stokes
> > equations. When using ILU as the subdomain preconditioner, I notice
> > convergence problems in the partition boundaries.
>
> I.e., it converges slowly there?  That is natural because the
> preconditioner is more accurate in the interior of subdomains.
>
> > This does not happen with the Jacobi preconditioner.
>
> Naturally, because Jacobi is identical regardless of the partition.
>
> > Do I need to provide any connectivity, node mapping, and/or overlap
> > information to Petsc before calling KSPsolve?
>
> No, the matrix is enough.
>
>


-- 
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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