recipe-blocking.cc

See explanation at Setting up blocked data structures

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <iostream>
 
#include <dune/common/filledarray.hh>
#include <dune/common/parallel/mpihelper.hh>
 
#include <dune/grid/yaspgrid.hh>
 
#include <dune/pdelab.hh>
 
 
int main(int argc, char** argv)
{
  // Initialize Mpi
  Dune::MPIHelper::instance(argc, argv);
 
  // need a grid in order to test grid functions
  constexpr unsigned int dim = 2;
  Dune::FieldVector<double,dim> L(5.0);
  std::array<int,dim> N(Dune::filledArray<dim,int>(64));
 
  typedef Dune::YaspGrid<dim> Grid;
  Grid grid(L,N);
 
  using DF = double;
  using GV = decltype(grid.leafGridView());
 
  // instantiate finite element maps
  typedef Dune::PDELab::QkLocalFiniteElementMap<GV,DF,double,1> FEM;
  FEM fem(grid.leafGridView());
 
  //Set up constraints
  typedef Dune::PDELab::ConformingDirichletConstraints Constraints;
 
  // [Scalar grid function space]
  // Set up scalar grid function space
  typedef Dune::PDELab::GridFunctionSpace<GV, FEM, Constraints, Dune::PDELab::ISTL::VectorBackend<>> SCALAR_GFS;
  SCALAR_GFS U1(grid.leafGridView(),fem); U1.name("U1");
  SCALAR_GFS U2(grid.leafGridView(),fem); U2.name("U2");
 
  {
  // [Lexiographic blocked type]
  // Use lexiographical blocked ordering
  typedef Dune::PDELab::LexicographicOrderingTag LexiographicOrderingTag;
 
  // Set up power grid function space
  using VBE = Dune::PDELab::ISTL::VectorBackend<Dune::PDELab::ISTL::Blocking::fixed>; // blocking vector backend
  typedef Dune::PDELab::PowerGridFunctionSpace<SCALAR_GFS,
                                                dim, // block size
                                                VBE, // blocked vector backend
                                                LexiographicOrderingTag> GFS;
  GFS gfs(U1,U2);
  }
 
  {
  // [Entity blocked type]
  // Use entity blocked ordering
  typedef Dune::PDELab::EntityBlockedOrderingTag EntityOrderingTag;
 
  // Setting up a composite grid function space with the same scalar grid function space in both components
  using VBE = Dune::PDELab::ISTL::VectorBackend<Dune::PDELab::ISTL::Blocking::fixed>; // blocking vector backend
  typedef Dune::PDELab::CompositeGridFunctionSpace<VBE, // blocked vector backend
                                                    EntityOrderingTag,
                                                    SCALAR_GFS, SCALAR_GFS> GFS;
  GFS gfs(U1,U2);
  }
}