dolfin team mailing list archive

["Johan Hoffman" <jhoffman@xxxxxxxxxx>]

> On Wed, Aug 13, 2008 at 2:57 PM, Johan Hoffman <jhoffman@xxxxxxxxxx>
> wrote:
>
>> >
>> >
>> > Johan Hoffman wrote:
>> >>>
>> >>> Anders Logg wrote:
>> >>>> On Tue, Jun 17, 2008 at 02:45:41PM +0100, Garth N. Wells wrote:
>> >>>>> It would be useful to lay out a plan for tackling DofMaps. Getting
>> >>>>> this
>> >>>>> right is the key to parallel assembly, assembly optimisations and
>> >>>>> applying Dirichlet boundary conditions by eliminating Dirichlet
>> dofs
>> >>>>> from the global system.
>> >>>>>
>> >>>>> I'm happy to take a look, but I'll need some time because I've
>> lost
>> >>>>> my
>> >>>>> overview of DofMaps. If someone else is already on top of it, I'd
>> be
>> >>>>> happy to provide feedback.
>> >>>>>
>> >>>>> Garth
>> >>>> I won't have time to look at it until after the summer and I
>> haven't
>> >>>> started.
>> >>>>
>> >>>> Anyway, I think we should wait until after the next release until
>> we
>> >>>> start messing with the dof maps.
>> >>>>
>> >>>> Are there any issues we need to sort out before releasing 0.8? I'm
>> >>>> thinking about a new release some time this or next week.
>> >>>>
>> >>>> One is to fix the bug in DirichletBC, but other than that?
>> >>>>
>> >>> Now would be a good time for a release so I can start messing with
>> >>> DofMaps.
>> >>>
>> >>> Garth
>> >>
>> >> Has anything more been done about the DofMap design? During the
>> summer
>> >> Niclas has extended to general elements his adaptive algorithm for
>> >> distributed parallel computing, so we are now ready to start messing
>> >> with
>> >> the DofMaps in order to implement his algorithm in DOLFIN.
>> >>
>> >
>> > It has been given some thought, but no changes have been made in the
>> > code yet.
>>
>> Ok. Any threads on the list to point to where this is discussed?
>>
>> If you have something already, I would suggest making it
>> > publicly available somewhere for feedback before starting work on
>> DOLFIN.
>>
>> It is a refinement and generalization of the thesis work of Niclas
>> Jansson
>> which was discussed on the list before the summer. Is is outlined in his
>> report:
>>
>> http://www.nada.kth.se/utbildning/grukth/exjobb/rapportlistor/2008/rapporter08/jansson_niclas_08051.pdf
>>
>> My announcement here was to initiate a discussion of the detailed
>> implementation, and to check if other DOLFIN-people were working on
>> similar stuff to avoid double/conflicting development.
>>
>> /Johan
>>
>
> Very good. We were about to start on this task, so now a good point in
> time
> to join forces.
> As a starting point, it would be nice to agreeing on what data is needed
> in
> addition to the partitioned meshes to construct the global dofmap. I.e.
> which MeshFunctions to construct during the mesh paritioning process. Are
> you people using the same {T,S,F} input as Anders describes in Algorithm 5
> in his paper?

We have discussed this, and it seems that for our adaptive algorithms we
need some more info. Basically, we have two aims:

1. Fully distributed computing (no collection of data on one processor)
2. Possibility for dynamic load balancing

To realize 1-2 we need information on the processor ownership of entities,
and for resdistributing the mesh we need global vertex numbering. That is,
we would need something like: {T,S,F,V,O}, where V is global vertex number
and O is information whether boundary (between processors) vertices are
own by the processor or if they are ghost nodes.

 Possibly this is too much information, since for example S,F can be
computed from V,O, but by storing all info faster algorithms can be
constructed, so there is a trad-off between speed and memory.

What do you say?

/Johan

>
>
> Ola
>
>
>>
>> >
>> > Garth
>> >
>> >
>> >> I see Anders report referenced in the code, where the mapping scheme
>> >> described is fairly close to what Niclas has implemented, although
>> there
>> >> are some differences. We will sit down today to sum up what we think
>> >> needs
>> >> to be done, and then we can discuss this on the mailing list.
>> >>
>> >> /Johan
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>> >
>> > _______________________________________________
>> > DOLFIN-dev mailing list
>> > DOLFIN-dev@xxxxxxxxxx
>> > http://www.fenics.org/mailman/listinfo/dolfin-dev
>> >
>>
>>
>> _______________________________________________
>> DOLFIN-dev mailing list
>> DOLFIN-dev@xxxxxxxxxx
>> http://www.fenics.org/mailman/listinfo/dolfin-dev
>>
>
>
>
> --
> Ola Skavhaug
>