Re: mesh ordering and partition

["Matthew Knepley" <knepley@xxxxxxxxx>]

On Fri, May 16, 2008 at 10:47 AM, Gong Ding <gdiso@xxxxxxxx> wrote:
> Hi,
> I am studying the parallel programming, using libmesh/petsc as an excellent
> example.
>
> I have some questions about the partition and mesh ordering.
>
>
>
> It seems libmesh does not reorder the mesh nodes. It only calls metis to
> partition the mesh, and
>
> uses original node order to build the matrix. I wonder if a bad mesh
> ordering may cause low efficency
>
> of ILU preconditioner. However, If I did RCM ordering to the mesh, the
> node's order may conflict with
>
> contiguous index set int the subdomain partitioned by metis. How should I
> balance the ordering (to reduce filling)
>
> and partition (to reduce communication)? any good ideas?

I think, if you are using the serial PETSc ILU, you should just use a
MatOrdering,
which can be done from the command line:

  -pc_type ilu -pc_factor_mat_ordering_type rcm

which I tested on KSP ex2.

  Matt

> Regards,
>
> Gong Ding
>
>
>
>
>



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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