[Dune] Use of partition iterators

[Steffen Müthing]

Hi Ganesh,


> Am 16.09.2015 um 19:14 schrieb Ganesh Diwan <gcdiwan83 at gmail.com>:
> 
> Sorry to bother you again,
> 
> If I set the iterator for vertices same as above, I am able to extract the border vertices but this obviously misses the domain boundary.
> I.e. it->partitionType()==Dune::BorderEntity gives me the shared vertices between the partition boundaries but not those on the domain boundary.

if you want to find the set of all vertices that are situated on the surface of the interiorBorder partition, the easiest way is probably to go through the
cells and their intersections:

for (const auto& cell : cells(gv,Partitions::interiorBorder))
{
  auto& ref_el = Dune::ReferenceElements<double,dim>::general(cell.geometry().type());
  for (const auto& is : intersections(gv,cell))
  {
    // this skips all intersections that are not either on the domain boundary or have a neighbor
    // that is not in the interior partition
    if ((!is.boundary()) || (is.neighbor() && is.outside().partitionType() == Dune::InteriorEntity))
      continue;
    for (int i = 0; i < ref_el.size(is.indexInInside(),1,dim); ++i)
    {
      auto local_vertex_index = ref_el.index(is.indexInInside(),1,i,dim);
      // here, you get every vertex that lies on the surface of the interiorBorder partition
      auto vertex = cell.template subEntity<dim>(local_vertex_index);
      // if you only need the index of that vertex, it is faster to do the following:
      auto vertex_index = gv.indexSet().subIndex(cell,local_vertex_index,dim);
    }
  }
}

That code isn’t tested, but it should be broadly correct. Note, however, that it can (and probably) will visit vertices multiple times!

Cheers,
Steffen

> 
> Thank you
> Ganesh
> 
> On Wed, Sep 16, 2015 at 5:30 PM, Ganesh Diwan <gcdiwan83 at gmail.com> wrote:
> Hi
> Thank you for your replies.
> 
> It appears that I can iterate through only the Ghost and InteriorEntity for codim 0 for a given partition. This is OK as I am concerned about the elements that are truly interior to a partition.
> I however need more information: how to extract all the vertices and edges (marked as blue in grid-howto) only on the border of the partition using this?
> 
> The border of partition must include the domain boundary if any (If I understand correctly, as per howto some of the edges/vertices can be of partitiontype interior and be on the domain boundary- aptly therefore marked red).
> 
> As of now, I am able to extract only the domain boundary edges in the partition this way.
> 
>     const Dune::PartitionIteratorType pit_all=Dune::All_Partition  ;
>     typedef typename GridType::template Codim<0>::template Partition<pit_all>::LeafIterator AllElementIterator;
>     typedef typename GridView::IntersectionIterator IntersectionIterator;
> 
>     int all_ElmCount = 0;
>     for (AllElementIterator it = grid.template leafbegin<0,pit_all>(); it!=grid.template leafend<0,pit_all>(); ++it) {
>         if (it->partitionType() == Dune::GhostEntity)
>             continue;
>         IntersectionIterator isIt = gv.ibegin(*it);
>         const IntersectionIterator &isEndIt = gv.iend(*it);
>         int numedges_on_domain_boundary = 0;
>         std::cout << "coe: " << it->geometry().center() << std::endl;
>         for (; isIt != isEndIt; ++isIt) {
>             if(isIt->boundary()) ++ numedges_on_domain_boundary;
>         }
>         std::cout << "edges on domain boundary = " << numedges_on_domain_boundary << std::endl;
>         ++all_ElmCount;
>     }
> 
> 
> One way to probe the border entities, I thought was to follow test-parallel-ug.cc code:
> 
> typedef Dune::MultipleCodimMultipleGeomTypeMapper<GridView, LayoutWrapper<0>::template Layout>
>     MapperType;
>     MapperType mapper(gv);
> 
> 
> and then probe the entity as:
> 
> for (AllElementIterator it = grid.template leafbegin<0,pit_all>(); it!=grid.template leafend<0,pit_all>(); ++it) { // element loop 2001
>         int numberOfSubEntities = it->template count<1>();
>         std::cout << "no of subentities = " << numberOfSubEntities << std::endl;
>         for (int k = 0; k < numberOfSubEntities; k++)
>         {
>             typedef typename GridView::template Codim<0>::Entity Element;
>             typedef typename Element::template Codim<0>::EntityPointer EntityPointer;
>             const EntityPointer entityPointer(it->template subEntity<1>(k)); // <<========= compilation error occurs here
>             entityIndex[mapper.map(*entityPointer)]   = mapper.map(*entityPointer);
> }
> }
> 
> But I have problem compiling this where I define the EntityPointer, the error is:
> 
>  error: no matching function for call to ‘Dune::EntityPointer<const Dune::UGGrid<2>, Dune::UGGridEntityPointer<0, const Dune::UGGrid<2> > >::EntityPointer(Dune::Entity<0, 2, const Dune::UGGrid<2>, Dune::UGGridEntity>::subentity_return_info<1>::type)’
>     const EntityPointer entityPointer(it->template subEntity<1>(k));
> 
> 
> Thank you,
> Ganesh
> 
> On Tue, Sep 15, 2015 at 5:38 PM, Markus Blatt <markus at dr-blatt.de> wrote:
> On Tue, Sep 15, 2015 at 02:42:47PM +0200, Jö Fahlke wrote:
> >
> > To unify things, and to make using the vertices() and elements() functions
> > easier, recently a new scheme for naming partitions was introduced[4].  The
> > new scheme makes it possible to name name all possible combinations, even
> > though not all combinations are supported or are even meaningful in the
> > context of entity iterators or communication.
> 
> Isn't that against the principles DUNE ("one algorithm to use them
> (grids) all"?)?
> 
> Can one query what combinations are supported by a grid?
> 
> Markus
> --
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> 
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> Hans-Bunte-Str. 8-10, 69123 Heidelberg, Germany
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> 
> 
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