[dune-pdelab] Nonoverlapping solver backend for implicit time-steppers

[Steffen Müthing]

Hi Jared,

what do you mean by parallelizing the system? I assume you ran this in parallel,
and that's when the problems cropped up?

Having said that, your example uses a nonoverlapping solver, not an overlapping
one as per Christian's suggestion. For DG, that won't work just like that, as the
per-processor domains are not coupled in any way (with nonoverlapping assembly,
the processes only share DOFs with codim > 0, those attached to a Border entity in
Dune-speak, and you don't have any DOFs of that type with a DG method). I'd suggest
you switch to an overlapping method like Christian said.

Apart from that, you cannot use the nonoverlapping Jacobi preconditioner here, as
the nonoverlapping Jacobi implementation in PDELab currently is not block-aware
and will thus not invert the dense DG blocks on the diagonal, but only the diagonal
of those blocks.

Steffen


Am 30.10.2012 um 10:25 schrieb Jared Okiro:

> On 10/19/2012 10:15 PM, Christian Engwer wrote:
>> UG provides a ghost layer, which should be sufficient for overlamming
>> parallelization using DG methods, as they are cell-based.
>> 
>> regarding the edge communication and UG you have to be more specific,
>> as "but it doesn't work for me" is not sufficient for us to guess what
>> the problem might be.
>> 
>> Christian
>> 
>> On Fri, Oct 19, 2012 at 06:27:56PM +0200, Jared Okiro wrote:
>>> Dear PDELab Members,
>>> 
>>> I am solving a reaction-diffusion system with more than two
>>> equations in 2D using
>>> Interior Penalty DG methods on UG grid. The sequential version works
>>> well, but if I try the parallel
>>> version, I get the error "missing edge communication". I saw
>>> sometime that edge communication was
>>> implemented in UG but it doesn't work for me.  The linear solver
>>> fails from the first iteration.
>>> I am still new to DUNE and in particular parallel implementation. I
>>> am inquiring if there is any example
>>> available for Nonoverlapping solvers with implicit time integrators
>>> which I can refer to. If not, then I will appreciate any advice.
>>> Thank you.
>>> 
>>> Kind regards,--
>>> 
>>> Jared Ouma Okiro,
>>> Institute for Analysis and Numerics,
>>> Otto-von- Guericke Universität,
>>> Universitätsplatz 02, Gebaude 02 / 115
>>> 39106 Magdeburg, Germany
>>> Office Tel: +493916712660
>>> Fax:        +493916718073
>>> Mobile:     +4917657479787
>>> Home Tel:   +4939155917376
>>> 
>>> 
>>> _______________________________________________
>>> dune-pdelab mailing list
>>> dune-pdelab at dune-project.org
>>> http://lists.dune-project.org/mailman/listinfo/dune-pdelab
>>> 
> Dear Christian,
> Thank you for the information. I decided to do a test case for a scalar problem before parallelizing the system. Attached is the test case. In this test case only one time step is solved and one can see that
> it produces the wrong solution at the processor boundaries.
> I would be grateful for any further assistance.
> Thank you.
> 
> -- 
> Jared Ouma Okiro,
> Institute for Analysis and Numerics,
> Otto-von- Guericke Universität,
> Universitätsplatz 02, Gebaude 02 / 115
> 39106 Magdeburg, Germany
> Office Tel: +493916712660
> Fax:        +493916718073
> Mobile:     +4917657479787
> Home Tel:   +4939155917376
> 
> <nonlinearproblem.cc><nonlinearproblem.hh>_______________________________________________
> dune-pdelab mailing list
> dune-pdelab at dune-project.org
> http://lists.dune-project.org/mailman/listinfo/dune-pdelab

Steffen Müthing
Universität Stuttgart
Institut für Parallele und Verteilte Systeme
Universitätsstr. 38
70569 Stuttgart
Tel: +49 711 685 88429
Fax: +49 711 685 88340
Email: steffen.muething at ipvs.uni-stuttgart.de

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