partitioner.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2024 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_PARTITIONER_H
#define LIBMESH_PARTITIONER_H

// Local Includes
#include "libmesh/libmesh.h"
#include "libmesh/id_types.h"
#include "libmesh/mesh_base.h" // for MeshBase::element_iterator

// C++ Includes
#include <cstddef>
#include <memory>
#include <unordered_map>
#include <queue>

namespace libMesh
{

// Forward Declarations
class ErrorVector;
enum PartitionerType : int;

class Partitioner
{
public:

  Partitioner () : _weights(nullptr) {}

  Partitioner (const Partitioner &) = default;
  Partitioner (Partitioner &&) = default;
  Partitioner & operator= (const Partitioner &) = default;
  Partitioner & operator= (Partitioner &&) = default;
  virtual ~Partitioner() = default;

  virtual PartitionerType type () const;

  static std::unique_ptr<Partitioner>
  build(const PartitionerType solver_package);

  virtual std::unique_ptr<Partitioner> clone () const = 0;

  virtual void partition (MeshBase & mesh,
                          const unsigned int n);

  virtual void partition (MeshBase & mesh);

  virtual void partition_range (MeshBase & /*mesh*/,
                                MeshBase::element_iterator /*beg*/,
                                MeshBase::element_iterator /*end*/,
                                const unsigned int /*n_parts*/)
  { libmesh_not_implemented(); }

  void repartition (MeshBase & mesh,
                    const unsigned int n);

  void repartition (MeshBase & mesh);

  static void partition_unpartitioned_elements (MeshBase & mesh);

  static void partition_unpartitioned_elements (MeshBase & mesh,
                                                const unsigned int n);

  static void set_parent_processor_ids(MeshBase & mesh);

  static void set_node_processor_ids(MeshBase & mesh);

  static void processor_pairs_to_interface_nodes(MeshBase & mesh, std::map<std::pair<processor_id_type, processor_id_type>, std::set<dof_id_type>> & processor_pair_to_nodes);

  static void set_interface_node_processor_ids_linear(MeshBase & mesh);

  static void set_interface_node_processor_ids_BFS(MeshBase & mesh);


  static void set_interface_node_processor_ids_petscpartitioner(MeshBase & mesh);

  virtual void attach_weights(ErrorVector * /*weights*/) { libmesh_not_implemented(); }

protected:

  bool single_partition (MeshBase & mesh);

  bool single_partition_range(MeshBase::element_iterator it,
                              MeshBase::element_iterator end);

  virtual void _do_partition(MeshBase & mesh,
                             const unsigned int n) = 0;

  virtual void _do_repartition (MeshBase & mesh,
                                const unsigned int n) { this->_do_partition (mesh, n); }

  static const dof_id_type communication_blocksize;

   virtual void _find_global_index_by_pid_map(const MeshBase & mesh);


  virtual void build_graph(const MeshBase & mesh);

  void assign_partitioning (MeshBase & mesh, const std::vector<dof_id_type> & parts);

  ErrorVector * _weights;

  std::unordered_map<dof_id_type, dof_id_type> _global_index_by_pid_map;

  std::vector<dof_id_type> _n_active_elem_on_proc;

  std::vector<std::vector<dof_id_type>> _dual_graph;


  std::vector<Elem *> _local_id_to_elem;
};

} // namespace libMesh

#endif // LIBMESH_PARTITIONER_H