Using parMetis in petsc for ordering

[Matthew Knepley]

Reordering a matrix can result in fewer iterations for an iterative solver.

  Matt

On 1/11/07, Dimitri Lecas <dimitri.lecas at free.fr> wrote:
> Barry Smith a écrit :
> >
> >
> > On Thu, 11 Jan 2007, Dimitri Lecas wrote:
> >
> >
> >> Barry Smith a �crit :
> >>
> >>>   Dimitri,
> >>>
> >>>    No, I think this is not the correct way to look at things. Load
> >>> balancing the original matrix is not neccessarily a good thing for
> >>> doing an LU factorization (in fact it is likely just to make the LU
> >>> factorization have much more fill and require much more floating
> >>> operations).
> >>>   Packages like SuperLU_dist and Mumps have their own internal ordering
> >>> routines that are specifically for getting a good ordering for doing
> >>> the parallel LU factorization, you should just have these solvers
> >>> use them (which they do automatically).
> >>>
> >>>    Barry
> >>>
> >>>
> >>> On Thu, 11 Jan 2007, Dimitri Lecas wrote:
> >>>
> >>>
> >>>
> >> I'am no longer talking about doing LU factorization. But use iterative method
> >> for solving a linear system, like bicg. Like in the ex10. In this example i
> >> don't understand why using MatPartitioning.
> >>
> >
> >   Please rephrase the question. Are you asking why one should do the partition
> > or why one should not? Are you asking in the case where the matrix is read from
> > disk or generated in a parallel program?
> >
> >
> I try to understand the interest to call MatPartitioning before solving
> the linear system with the same matrix. (Like
> ksp/examples/tutorials/ex10.c).
>
> --
> Dimitri Lecas
>
>


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