topology_map.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2019 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner
 
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
 
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
 
 
#ifndef LIBMESH_TOPOLOGY_MAP_H
#define LIBMESH_TOPOLOGY_MAP_H
 
// Local Includes
#include "libmesh/libmesh_config.h"
#include "libmesh/libmesh_common.h"
 
// C++ Includes
#include <unordered_map>
#include <functional> // std::hash
#include <vector>
 
namespace libMesh
{
 
// Forward Declarations
class Elem;
class MeshBase;
class Node;
 
// Fix for STL laziness
struct myhash {
public:
  template <typename T1, typename T2>
  std::size_t operator()(const std::pair<T1, T2> & x) const
  {
    // recommendation from
    // http://stackoverflow.com/questions/5889238/why-is-xor-the-default-way-to-combine-hashes
    return 3 * std::hash<T1>()(x.first) + std::hash<T2>()(x.second);
  }
};
 
class TopologyMap
{
  // We need to supply our own hash function.
  typedef std::unordered_map<std::pair<dof_id_type, dof_id_type>, dof_id_type, myhash> map_type;
public:
  void init(MeshBase &);
 
  void clear() { _map.clear(); }
 
  void add_node(const Node & mid_node,
                const std::vector<
                std::pair<dof_id_type, dof_id_type>> &
                bracketing_nodes);
 
  bool empty() const { return _map.empty(); }
 
  dof_id_type find(dof_id_type bracket_node1,
                   dof_id_type bracket_node2) const;
 
  dof_id_type find(const std::vector<
                   std::pair<dof_id_type, dof_id_type>> &
                   bracketing_nodes) const;
 
protected:
  void fill(const MeshBase &);
 
private:
  map_type          _map;
};
 
} // namespace libMesh
 
 
#endif // LIBMESH_TOPOLOGY_MAP_H