dolfin team mailing list archive

[Niclas Jansson <njansson@xxxxxxxxxx>]

Anders Logg <logg@xxxxxxxxx> writes:

> On Tue, Feb 01, 2011 at 11:57:28AM -0000, Anders Logg wrote:
>> Question #143645 on DOLFIN changed:
>> https://answers.launchpad.net/dolfin/+question/143645
>>
>> Anders Logg proposed the following answer:
>> On Tue, Feb 01, 2011 at 11:50:37AM -0000, Garth Wells wrote:
>> > Question #143645 on DOLFIN changed:
>> > https://answers.launchpad.net/dolfin/+question/143645
>> >
>> >     Status: Open => Answered
>> >
>> > Garth Wells proposed the following answer:
>> > I don't think so.
>>
>> I think it should be possible, at least "in principle". I'll comment
>> more later. I'm in a meeting now.
>
> Sorry for my late reply.
>
> What you can do is to get the "overlap":
>
> std::map<uint, std::vector<uint> >* overlap = mesh.data().vector_mapping("overlap");
>
> This gives you a mapping for each shared vertex to its neighboring
> processes (the processes it's shared with).
>
> You can check if a vertex is shared by
>
>   overlap->find(i) != overlap->end()
>
> There is no functionality for checking edges, cells etc. Such
> operations must be expressed in terms of their vertices.
>
> It would be easy to add some shortcuts like
>
>   bool Vertex::is_ shared() const;
>
> and even
>
>   bool MeshEntity::is_shared() const;
>
> etc if that helps. They could just look at the overlap.
>
> If that is costly, we could store another MeshFunction that holds the
> appropriate data (or add as part of ParallelData).
>
> --
> Anders
>

Perfect! That should be enough to get me started porting some code.

How about owners of mesh entities? If I remember correctly mesh entities
were not owned by a specific rank. If one could determine if a vertex
is owned, ghosted or shared, it would make life much simpler when
implementing various parallel mesh algorithms.


Niclas