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

[Andreas Lauser]

Hi Rebecca,

Thank you for the quick and helpful answer. I have to annoy you with an 
additional question, though: For entities on the border, is there only one 
owner or are all processes which are adjacent to a border entity its owners? I 
tried to figure that out using PDELab's ParallelIstlHelper, but that code 
defeated me...

cheers
  Andreas

Am Donnerstag, 6. September 2012, 18:36:44 schrieb 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
> 
> > 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
> 
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-- 
Andreas Lauser
Department of Hydromechanics and Modelling of Hydrosystems
University of Stuttgart
Pfaffenwaldring 61
D-70569 Stuttgart
Phone: (+49) 711 685-64719
Fax: (+49) 711 685-60430
www.hydrosys.uni-stuttgart.de