/**
 * @file   discretization_poisson_fd_collatz.hpp
 * @author Julian Iseringhausen <isering@ins.uni-bonn.de>
 * @date   Mon Apr 18 13:02:26 2011
 *
 * @brief  Collatz finite difference discretization of the
 *         Poisson equation for a higher order discretization
 *         while preserving compactness of the stencil.
 *
 */

#ifndef DISCRETIZATION_POISSON_FD_COLLATZ_HPP_
#define DISCRETIZATION_POISSON_FD_COLLATZ_HPP_

#include "base/discretization.hpp"

namespace VMG
{

class DiscretizationPoissonFDCollatz : public Discretization
{
public:
  DiscretizationPoissonFDCollatz()
  {
    stencil.SetDiag(24.0/6.0);

    stencil.push_back(-1,  0,  0, -2.0/6.0);
    stencil.push_back( 1,  0,  0, -2.0/6.0);
    stencil.push_back( 0, -1,  0, -2.0/6.0);
    stencil.push_back( 0,  1,  0, -2.0/6.0);
    stencil.push_back( 0,  0, -1, -2.0/6.0);
    stencil.push_back( 0,  0,  1, -2.0/6.0);

    stencil.push_back(-1, -1,  0, -1.0/6.0);
    stencil.push_back(-1,  1,  0, -1.0/6.0);
    stencil.push_back( 1, -1,  0, -1.0/6.0);
    stencil.push_back( 1,  1,  0, -1.0/6.0);
    stencil.push_back(-1,  0, -1, -1.0/6.0);
    stencil.push_back(-1,  0,  1, -1.0/6.0);
    stencil.push_back( 1,  0, -1, -1.0/6.0);
    stencil.push_back( 1,  0,  1, -1.0/6.0);
    stencil.push_back( 0, -1, -1, -1.0/6.0);
    stencil.push_back( 0, -1,  1, -1.0/6.0);
    stencil.push_back( 0,  1, -1, -1.0/6.0);
    stencil.push_back( 0,  1,  1, -1.0/6.0);
  }

  vmg_float OperatorPrefactor(const Multigrid& grid) const
  {
    return 1.0 / (sqr(grid.MeshWidth()));
  }

private:
  void SetInnerBoundaryCompute(Multigrid& grid) const {}
};

class StencilPoissonCollatzRhs : public Stencil
{
public:
  StencilPoissonCollatzRhs() : Stencil(0.5)
  {
    this->push_back(Displacement(-1,  0,  0, 1.0/12.0));
    this->push_back(Displacement( 1,  0,  0, 1.0/12.0));
    this->push_back(Displacement( 0, -1,  0, 1.0/12.0));
    this->push_back(Displacement( 0,  1,  0, 1.0/12.0));
    this->push_back(Displacement( 0,  0, -1, 1.0/12.0));
    this->push_back(Displacement( 0,  0,  1, 1.0/12.0));
  }
};

}

#endif /* DISCRETIZATION_POISSON_FD_HPP_ */