boundaryidprovider.hh

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#ifndef DUNE_FEM_MISC_BOUNDARYIDPROVIDER_HH
#define DUNE_FEM_MISC_BOUNDARYIDPROVIDER_HH
 
#include <dune/common/exceptions.hh>
#include <dune/common/typeutilities.hh>
 
#include <dune/grid/common/capabilities.hh>
 
#include <dune/fem/function/common/localcontribution.hh>
 
namespace Dune
{
  namespace Fem
  {
 
    template< class Grid >
    struct BoundaryIdProvider
    {
      template< class Intersection >
      static int boundaryId ( const Intersection &intersection )
      {
        // for all grids that have the method, call it on the implementation
        if constexpr ( requires{ intersection.impl().boundaryId(); })
        {
          return intersection.impl().boundaryId();
        }
        else // otherwise use fallback
        {
          // Cartesian grids use indexInInside + 1
          if constexpr ( Dune::Capabilities::isCartesian< Grid > :: v )
          {
            return (intersection.boundary() ? (intersection.indexInInside()+1) : 0);
          }
          else // e.g. UGGrid
          {
            return intersection.boundarySegmentIndex();
          }
        }
      }
    };
 
    // BoundaryIdProvider for general GridParts or GridViews
    // -----------------------------------------------------
 
    template< class GridView, class Intersection>
    inline static int boundaryId ( const Intersection &intersection )
    {
      return Dune::Fem::BoundaryIdProvider< typename GridView::Grid > ::
             boundaryId( intersection );
    }
 
    template< class GridView, class Intersection>
    inline static int boundaryId ( const GridView&, const Intersection &intersection )
    {
      return Dune::Fem::BoundaryIdProvider< typename GridView::Grid > ::
             boundaryId( intersection );
    }
 
 
    /* \brief BoundaryId inspection: project boundary ids to piecewise constant
              function. Elements with more than one boundary segment will
              contain the sum of all boundary ids.
    */
    template <class DiscreteFunction>
    void projectBoundaryIds( DiscreteFunction& df )
    {
      if( df.space().order() != 0 ) // should be piecewise constant, and FV space
      {
        DUNE_THROW(InvalidStateException,"projectBoundaryIds: expect piecewise constant discrete function");
      }
 
      df.clear(); // reset all dofs
 
      const auto& gridPart = df.space().gridPart();
 
      typedef AddLocalContribution< DiscreteFunction > AddLocalContributionType;
      AddLocalContributionType localDf( df );
      for( const auto& element : df.space() )
      {
        int count = 0;
        auto guard = bindGuard( localDf, element );
        for( const auto& intersection : intersections( gridPart, element ) )
        {
          if( intersection.boundary() )
          {
            localDf[ 0 ] += boundaryId( gridPart, intersection );
            count += 1;
          }
        }
        if (count>0)
          localDf[ 0 ] /= double(count);
      }
    }
 
  } // namespace Fem
 
} // namespace Dune
 
#endif // #ifndef DUNE_FEM_MISC_BOUNDARYIDPROVIDER_HH