structuredgridfactory.hh

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// SPDX-FileCopyrightText: Copyright (C) DUNE Project contributors, see file LICENSE.md in module root
// SPDX-License-Identifier: LicenseRef-GPL-2.0-only-with-DUNE-exception
// -*- tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
// vi: set et ts=4 sw=2 sts=2:
 
#ifndef DUNE_ALBERTA_STRUCTUREDGRIDFACTORY_HH
#define DUNE_ALBERTA_STRUCTUREDGRIDFACTORY_HH
 
#include <array>
#include <memory>
#include <vector>
#include <tuple>
 
#include <dune/common/exceptions.hh>
#include <dune/common/fvector.hh>
#include <dune/grid/common/gridfactory.hh>
#include <dune/grid/utility/multiindex.hh>
#include <dune/grid/utility/structuredgridfactory.hh>
 
#if HAVE_ALBERTA
 
namespace Dune
{
  // Forward Declarations
  template <class Grid>
  class StructuredGridFactory;
 
  template <int dim, int dimworld>
  class AlbertaGrid;
 
  template <int dim, int dimworld>
  class StructuredGridFactory<AlbertaGrid<dim,dimworld>>
  {
    using GridType = AlbertaGrid<dim,dimworld>;
 
  protected:
    using ctype = typename GridType::ctype;
 
    // Insert new elements into the grid by splitting the given cube with corners `vertices` into
    // a curresponding number of simplices.
    static void insertElement (GridFactory<GridType>& factory,
      const GeometryType& type,
      const std::vector<unsigned int>& vertices)
    {
      // triangulation of reference cube
      static const auto reference_cubes = std::make_tuple(
        /*1d*/ std::array{std::array{0,1}},
        /*2d*/ std::array{std::array{3,0,1}, std::array{0,3,2}},
        /*3d*/ std::array{std::array{0,7,3,1}, std::array{0,7,5,1},
                          std::array{0,7,5,4}, std::array{0,7,3,2},
                          std::array{0,7,6,2}, std::array{0,7,6,4}} );
 
      const auto& simplices = std::get<dim-1>(reference_cubes);
      std::vector<unsigned int> corners(dim+1);
      for (const auto& simplex : simplices) {
        for (std::size_t i = 0; i < simplex.size(); ++i)
          corners[i] = vertices[simplex[i]];
 
        factory.insertElement(type, corners);
      }
    }
 
    // Insert a structured set of vertices into the factory
    static void insertVertices (GridFactory<GridType>& factory,
      const FieldVector<ctype,dimworld>& lowerLeft,
      const FieldVector<ctype,dimworld>& upperRight,
      const std::array<unsigned int,dim>& vertices)
    {
      FactoryUtilities::MultiIndex<dim> index(vertices);
 
      // Compute the total number of vertices to be created
      int numVertices = index.cycle();
 
      // Create vertices
      for (int i=0; i<numVertices; i++, ++index) {
 
        // scale the multiindex to obtain a world position
        FieldVector<double,dimworld> pos(0);
        for (int j=0; j<dim; j++)
          pos[j] = lowerLeft[j] + index[j] * (upperRight[j]-lowerLeft[j])/(vertices[j]-1);
        for (int j=dim; j<dimworld; j++)
          pos[j] = lowerLeft[j];
 
        factory.insertVertex(pos);
 
      }
 
    }
 
    // Compute the index offsets needed to move to the adjacent vertices
    // in the different coordinate directions
    static std::array<unsigned int, dim> computeUnitOffsets (
      const std::array<unsigned int,dim>& vertices)
    {
      std::array<unsigned int, dim> unitOffsets;
      if (dim>0)        // paranoia
        unitOffsets[0] = 1;
 
      for (int i=1; i<dim; i++)
        unitOffsets[i] = unitOffsets[i-1] * vertices[i-1];
 
      return unitOffsets;
    }
 
  public:
    static void createSimplexGrid (GridFactory<GridType>& factory,
      const FieldVector<ctype,dimworld>& lowerLeft,
      const FieldVector<ctype,dimworld>& upperRight,
      const std::array<unsigned int,dim>& elements)
    {
      if (factory.comm().rank() == 0)
      {
        // Insert uniformly spaced vertices
        std::array<unsigned int,dim> vertices = elements;
        for (std::size_t i=0; i<vertices.size(); ++i)
          vertices[i]++;
 
        insertVertices(factory, lowerLeft, upperRight, vertices);
 
        // Compute the index offsets needed to move to the adjacent
        // vertices in the different coordinate directions
        std::array<unsigned int, dim> unitOffsets =
          computeUnitOffsets(vertices);
 
        // Compute an element template (the cube at (0,...,0).  All
        // other cubes are constructed by moving this template around
        unsigned int nCorners = 1<<dim;
 
        std::vector<unsigned int> cornersTemplate(nCorners,0);
        for (std::size_t i=0; i<nCorners; ++i)
          for (int j=0; j<dim; ++j)
            if ( i & (1<<j) )
              cornersTemplate[i] += unitOffsets[j];
 
        // Insert elements
        FactoryUtilities::MultiIndex<dim> index(elements);
 
        // Compute the total number of elements to be created
        int numElements = index.cycle();
 
        for (int i=0; i<numElements; ++i, ++index) {
 
          // 'base' is the index of the lower left element corner
          unsigned int base = 0;
          for (int j=0; j<dim; j++)
            base += index[j] * unitOffsets[j];
 
          // insert new element
          std::vector<unsigned int> corners = cornersTemplate;
          for (std::size_t j=0; j<corners.size(); ++j)
            corners[j] += base;
 
          insertElement(factory, GeometryTypes::simplex(dim), corners);
        }
      }
    }
 
    static std::unique_ptr<GridType> createSimplexGrid (
      const FieldVector<ctype,dimworld>& lowerLeft,
      const FieldVector<ctype,dimworld>& upperRight,
      const std::array<unsigned int,dim>& elements)
    {
      GridFactory<GridType> factory;
      createSimplexGrid(factory, lowerLeft, upperRight, elements);
      return std::unique_ptr<GridType>(factory.createGrid());
    }
 
 
    static void createCubeGrid (GridFactory<GridType>& factory,
      const FieldVector<ctype,dimworld>& lowerLeft,
      const FieldVector<ctype,dimworld>& upperRight,
      const std::array<unsigned int,dim>& elements)
    {
      DUNE_THROW(Dune::NotImplemented,
        "Cube grids are not supported by AlbertaGrid. Use createSimplexGrid instead.");
    }
 
    static std::unique_ptr<GridType> createCubeGrid (
      const FieldVector<ctype,dimworld>& lowerLeft,
      const FieldVector<ctype,dimworld>& upperRight,
      const std::array<unsigned int,dim>& elements)
    {
      DUNE_THROW(Dune::NotImplemented,
        "Cube grids are not supported by AlbertaGrid. Use createSimplexGrid instead.");
      return nullptr;
    }
  };
 
} // end namespace Dune
 
#endif // HAVE_ALBERTA
 
#endif // DUNE_ALBERTA_STRUCTUREDGRIDFACTORY_HH