mesh_communication.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2025 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_MESH_COMMUNICATION_H
#define LIBMESH_MESH_COMMUNICATION_H

// Local Includes
#include "libmesh/compare_elems_by_level.h"
#include "libmesh/libmesh_common.h"
#include "libmesh/mesh_base.h"

// C++ Includes
#include <set>
#include <utility>
#include <unordered_map>
#include <vector>

namespace libMesh
{

// Forward declarations
class MeshBase;
class DistributedMesh;

// This is for backwards compatibility, but if your code relies on
// forward declarations in our headers then fix it.
class ParallelMesh;

class MeshCommunication
{
public:

  MeshCommunication () = default;

  ~MeshCommunication () = default;

  void clear ();

  //   /**
  //    * Finds all the processors that may contain
  //    * elements that neighbor my elements.  This list
  //    * is guaranteed to include all processors that border
  //    * any of my elements, but may include additional ones as
  //    * well.  This method computes bounding boxes for the
  //    * elements on each processor and checks for overlaps.
  //    */
  //   void find_neighboring_processors(const MeshBase &);

  void broadcast (MeshBase &) const;

  void redistribute (DistributedMesh & mesh,
                     bool newly_coarsened_only = false) const;

  void gather_neighboring_elements (DistributedMesh &) const;

  void send_coarse_ghosts (MeshBase &) const;

  void gather (const processor_id_type root_id, MeshBase &) const;

  void allgather (MeshBase & mesh) const
  { MeshCommunication::gather(DofObject::invalid_processor_id, mesh); }

  void delete_remote_elements (DistributedMesh &, const std::set<Elem *> &) const;

  void assign_global_indices (MeshBase &) const;

  void check_for_duplicate_global_indices (MeshBase & ) const;

  template <typename ForwardIterator>
  void find_local_indices (const libMesh::BoundingBox &,
                           const ForwardIterator &,
                           const ForwardIterator &,
                           std::unordered_map<dof_id_type, dof_id_type> &) const;

  template <typename ForwardIterator>
  void find_global_indices (const Parallel::Communicator & communicator,
                            const libMesh::BoundingBox &,
                            const ForwardIterator &,
                            const ForwardIterator &,
                            std::vector<dof_id_type> &) const;

  void make_elems_parallel_consistent (MeshBase &);

#ifdef LIBMESH_ENABLE_AMR

  void make_p_levels_parallel_consistent (MeshBase &);
#endif // LIBMESH_ENABLE_AMR

  void make_node_ids_parallel_consistent (MeshBase &);

  void make_node_unique_ids_parallel_consistent (MeshBase &);

  void make_node_bcids_parallel_consistent (MeshBase &);

  void make_node_proc_ids_parallel_consistent (MeshBase &);

  void make_new_node_proc_ids_parallel_consistent (MeshBase &);

  void make_nodes_parallel_consistent (MeshBase &);

  void make_new_nodes_parallel_consistent (MeshBase &);
};


// Related utilities

// What to use to fill sets of connected nodes and elements
typedef std::set<const Node *> connected_node_set_type;
typedef std::set<const Elem *, CompareElemIdsByLevel> connected_elem_set_type;

// Ask a mesh's ghosting functors to insert into a set all elements
// that are either on or connected to processor id \p pid.  Ask only
// for elements in the range from \p elem_it before \p elem_end;
// typically this may be mesh.active_pid_elements_*(pid)
void query_ghosting_functors(const MeshBase & mesh,
                             processor_id_type pid,
                             MeshBase::const_element_iterator elem_it,
                             MeshBase::const_element_iterator elem_end,
                             connected_elem_set_type & connected_elements);

// Take a set of elements and insert all immediate
// children of elements in the given range
void connect_children(const MeshBase & mesh,
                      MeshBase::const_element_iterator elem_it,
                      MeshBase::const_element_iterator elem_end,
                      connected_elem_set_type & connected_elements);

// Take a set of elements and insert all elements' ancestors and
// subactive descendants as well.  If a mesh is provided and has any
// constraint rows, insert elements with the constraining nodes for
// any constrained nodes in our set.
//
// \deprecated This method is now deprecated, because it does not
// handle recursive dependencies.  Use the new
// connect_element_dependencies method instead.
#ifdef LIBMESH_ENABLE_DEPRECATED
void connect_families(connected_elem_set_type & connected_elements,
                      const MeshBase * mesh = nullptr);
#endif // LIBMESH_ENABLE_DEPRECATED

// Take a set of elements and create a set of connected nodes.
void reconnect_nodes (connected_elem_set_type & connected_elements,
                      connected_node_set_type & connected_nodes);

// Take a set of elements and of nodes, and insert all
// libMesh-mandated element of them: ancestor elements,
// immediate children, subactive descendents of active elements,
// interior_parents, nodes of any of those elements, and elements used
// to constrain any of those nodes.  This must be done recursively
// (well, repeatedly; we unroll) in the general case, since a node
// constraint can require a new element that can require other new
// elements with new nodes with new constraints.
void connect_element_dependencies(const MeshBase & mesh,
                                  connected_elem_set_type & connected_elements,
                                  connected_node_set_type & connected_nodes);

// Takes already-examined sets and not-yet-examined sets, returns more sets
// in need of examination (or empty sets if done).
std::pair<connected_elem_set_type, connected_node_set_type>
connect_element_dependencies(const MeshBase & mesh,
                             const connected_elem_set_type & connected_elements,
                             const connected_node_set_type & connected_nodes,
                             const connected_elem_set_type & new_connected_elements,
                             const connected_node_set_type & new_connected_nodes);

//--------------------------------------------------------------
// MeshCommunication inline members


} // namespace libMesh

#endif // LIBMESH_MESH_COMMUNICATION_H