[Dune-devel] Semantics of {ghost,overlap}Size

[Markus Blatt]

Hi,

On Thu, Nov 07, 2013 at 08:22:14PM +0100, Peter Bastian wrote:
>
> Codim dim (vertices) is needed for standard overlapping DD methods.
> I would define two vertices as connected if they are subentites of a common
> codim 0 entity. With that Graph defined the distance ist clear.
> Then of course the data decomposition is still with respect to codim 0
> entites
>
> 
> likewise two codim 0 entites are connected if they share an intersection.

Sounds reasonable.

Just to be sure: If I read the grid paper correctly, the following
holds: If the grid has overlap size 1 for codim 0 entities, then all
vertices attached to an overlap entity of codim 0 belong either to
the border or the front partition (even if there is an empty ghost
partition). This would make overlapSize of codim dim 0.  This was rather
unexspected when I came across it and seems to contradict the
implementation of the method in yaspgrid, where overlap size is the
same for all codims.

> I am not sure whether the "overlap size" has any real application. In the numerical
> methods it is usually not needed.

I was wondering about this, too.

> I am in favor of a meeting. Do you think about small cosmetic changes or something
> bigger? If it is bigger then we should also consider extensions due to hybrid
> parallelism, i.e. multithreading.
> 

BTW: I would be take part in such meeting.

Markus