[Dune] difference between OwnerOverlapCopyAttributeSet::copy and OwnerOverlapCopyAttributeSet::overlap

[Rebecca Neumann]

Hi Andreas,
that is right the attribute overlap is not used. For every degree of 
freedom that is shared with other processes, the owner attribute is used 
if the process is the owner, and else the copy attribute.
I think the overlap attribute is just there for historical reasons?
When I implemented nonoverlapping AMG I used the overlap attribute for 
the ghost degrees of freedom that do not lie on the  processor border.
Best Regards,
Rebecca

-- 
Rebecca Neumann
Universität Heidelberg
Interdisziplinäres Zentrum für Wissenschaftliches Rechnen
Im Neuenheimer Feld 368, 69120 Heidelberg
Tel: 06221/548890   Fax: 06221/548884
e-mail: <rebecca.neumann at iwr.uni-heidelberg.de>

On 06.09.2012 17:28, Andreas Lauser wrote:
> Hi Dune,
>
> Today I was wrestling with my and dune-istl's parallelization code once again.
> During that, I started to wonder what the difference between
> OwnerOverlapCopyAttributeSet::copy and OwnerOverlapCopyAttributeSet::overlap
> is. I could not find anything in the doxygen documentation, and the
> corrosponding lines in dune/istl/owneroverlapcopy.hh read:
>
> struct OwnerOverlapCopyAttributeSet
>    {
>          enum AttributeSet {
>            owner=1, overlap=2, copy=3 };
>    };
>
> what made me wonder even more, is that the code in
> dune/istl/paamg/test/anisotropic.hh (which creates the matrix for the parallel
> AMG test) does not use OwnerOverlapCopyAttributeSet::overlap even though the
> matrix which it creates clearly corresponds to one which stems from an
> overlapping grid. (if I understood that code correctly.)
>
> can anyone with deeper insight on ISTL tell the difference?
>
> cheers
>    Andreas
>