dof_handler.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 1998 - 2020 by the deal.II authors
//
// This file is part of the deal.II library.
//
// The deal.II library is free software; you can use it, 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.
// The full text of the license can be found in the file LICENSE.md at
// the top level directory of deal.II.
//
// ---------------------------------------------------------------------

#ifndef dealii_dof_handler_h
#define dealii_dof_handler_h



#include <deal.II/base/config.h>

#include <deal.II/base/exceptions.h>
#include <deal.II/base/function.h>
#include <deal.II/base/index_set.h>
#include <deal.II/base/iterator_range.h>
#include <deal.II/base/smartpointer.h>

#include <deal.II/distributed/tria_base.h>

#include <deal.II/dofs/block_info.h>
#include <deal.II/dofs/deprecated_function_map.h>
#include <deal.II/dofs/dof_accessor.h>
#include <deal.II/dofs/dof_faces.h>
#include <deal.II/dofs/dof_iterator_selector.h>
#include <deal.II/dofs/dof_levels.h>
#include <deal.II/dofs/number_cache.h>

#include <deal.II/hp/fe_collection.h>

#include <boost/serialization/split_member.hpp>

#include <map>
#include <memory>
#include <set>
#include <vector>

DEAL_II_NAMESPACE_OPEN

// Forward declarations
#ifndef DOXYGEN
template <int dim, int spacedim>
class FiniteElement;
template <int dim, int spacedim>
class Triangulation;

namespace internal
{
  namespace DoFHandlerImplementation
  {
    struct Implementation;

    namespace Policy
    {
      template <int dim, int spacedim>
      class PolicyBase;
      struct Implementation;
    } // namespace Policy
  }   // namespace DoFHandlerImplementation

  namespace DoFAccessorImplementation
  {
    struct Implementation;
  }

  namespace DoFCellAccessorImplementation
  {
    struct Implementation;
  }
} // namespace internal
#endif

template <int dim, int spacedim = dim>
class DoFHandler : public Subscriptor
{
  using ActiveSelector = ::internal::DoFHandlerImplementation::
    Iterators<DoFHandler<dim, spacedim>, false>;
  using LevelSelector = ::internal::DoFHandlerImplementation::
    Iterators<DoFHandler<dim, spacedim>, true>;

public:
  using cell_accessor = typename ActiveSelector::CellAccessor;

  using face_accessor = typename ActiveSelector::FaceAccessor;

  using line_iterator = typename ActiveSelector::line_iterator;

  using active_line_iterator = typename ActiveSelector::active_line_iterator;

  using quad_iterator = typename ActiveSelector::quad_iterator;

  using active_quad_iterator = typename ActiveSelector::active_quad_iterator;

  using hex_iterator = typename ActiveSelector::hex_iterator;

  using active_hex_iterator = typename ActiveSelector::active_hex_iterator;

  using active_cell_iterator = typename ActiveSelector::active_cell_iterator;

  using cell_iterator = typename ActiveSelector::cell_iterator;

  using face_iterator = typename ActiveSelector::face_iterator;

  using active_face_iterator = typename ActiveSelector::active_face_iterator;

  using level_cell_accessor = typename LevelSelector::CellAccessor;
  using level_face_accessor = typename LevelSelector::FaceAccessor;

  using level_cell_iterator = typename LevelSelector::cell_iterator;
  using level_face_iterator = typename LevelSelector::face_iterator;


  static const unsigned int dimension = dim;

  static const unsigned int space_dimension = spacedim;

  static const bool is_hp_dof_handler = false;

  static const unsigned int default_fe_index = 0;

  DoFHandler();

  DoFHandler(const Triangulation<dim, spacedim> &tria);

  DoFHandler(const DoFHandler &) = delete;

  virtual ~DoFHandler() override;

  DoFHandler &
  operator=(const DoFHandler &) = delete;

  void
  initialize(const Triangulation<dim, spacedim> &tria,
             const FiniteElement<dim, spacedim> &fe);

  virtual void
  set_fe(const FiniteElement<dim, spacedim> &fe);

  virtual void
  distribute_dofs(const FiniteElement<dim, spacedim> &fe);

  virtual void
  distribute_mg_dofs();

  bool
  has_level_dofs() const;

  bool
  has_active_dofs() const;

  void
  initialize_local_block_info();

  virtual void
  clear();

  void
  renumber_dofs(const std::vector<types::global_dof_index> &new_numbers);

  void
  renumber_dofs(const unsigned int                          level,
                const std::vector<types::global_dof_index> &new_numbers);

  unsigned int
  max_couplings_between_dofs() const;

  unsigned int
  max_couplings_between_boundary_dofs() const;

  /*--------------------------------------*/

  /*
   * @{
   */

  cell_iterator
  begin(const unsigned int level = 0) const;

  active_cell_iterator
  begin_active(const unsigned int level = 0) const;

  cell_iterator
  end() const;

  cell_iterator
  end(const unsigned int level) const;

  active_cell_iterator
  end_active(const unsigned int level) const;


  level_cell_iterator
  begin_mg(const unsigned int level = 0) const;

  level_cell_iterator
  end_mg(const unsigned int level) const;

  level_cell_iterator
  end_mg() const;

  IteratorRange<cell_iterator>
  cell_iterators() const;

  IteratorRange<active_cell_iterator>
  active_cell_iterators() const;

  IteratorRange<level_cell_iterator>
  mg_cell_iterators() const;

  IteratorRange<cell_iterator>
  cell_iterators_on_level(const unsigned int level) const;

  IteratorRange<active_cell_iterator>
  active_cell_iterators_on_level(const unsigned int level) const;

  IteratorRange<level_cell_iterator>
  mg_cell_iterators_on_level(const unsigned int level) const;

  /*
   * @}
   */


  /*---------------------------------------*/


  types::global_dof_index
  n_dofs() const;

  types::global_dof_index
  n_dofs(const unsigned int level) const;

  types::global_dof_index
  n_boundary_dofs() const;

  template <typename number>
  types::global_dof_index
  n_boundary_dofs(
    const std::map<types::boundary_id, const Function<spacedim, number> *>
      &boundary_ids) const;

  types::global_dof_index
  n_boundary_dofs(const std::set<types::boundary_id> &boundary_ids) const;

  const BlockInfo &
  block_info() const;


  types::global_dof_index
  n_locally_owned_dofs() const;

  const IndexSet &
  locally_owned_dofs() const;

  const IndexSet &
  locally_owned_mg_dofs(const unsigned int level) const;

  DEAL_II_DEPRECATED const std::vector<IndexSet> &
                           locally_owned_dofs_per_processor() const;

  DEAL_II_DEPRECATED const std::vector<types::global_dof_index> &
                           n_locally_owned_dofs_per_processor() const;

  DEAL_II_DEPRECATED const std::vector<IndexSet> &
                           locally_owned_mg_dofs_per_processor(const unsigned int level) const;

  const FiniteElement<dim, spacedim> &
  get_fe(const unsigned int index = 0) const;

  const hp::FECollection<dim, spacedim> &
  get_fe_collection() const;

  const Triangulation<dim, spacedim> &
  get_triangulation() const;

  virtual std::size_t
  memory_consumption() const;

  template <class Archive>
  void
  save(Archive &ar, const unsigned int version) const;

  template <class Archive>
  void
  load(Archive &ar, const unsigned int version);

#ifdef DOXYGEN

  template <class Archive>
  void
  serialize(Archive &archive, const unsigned int version);
#else
  // This macro defines the serialize() method that is compatible with
  // the templated save() and load() method that have been implemented.
  BOOST_SERIALIZATION_SPLIT_MEMBER()
#endif

  DeclException0(ExcGridsDoNotMatch);
  DeclException0(ExcInvalidBoundaryIndicator);
  DeclException1(ExcNewNumbersNotConsecutive,
                 types::global_dof_index,
                 << "The given list of new dof indices is not consecutive: "
                 << "the index " << arg1 << " does not exist.");
  DeclException1(ExcInvalidLevel,
                 int,
                 << "The given level " << arg1
                 << " is not in the valid range!");
  DeclException0(ExcFacesHaveNoLevel);
  DeclException1(ExcEmptyLevel,
                 int,
                 << "You tried to do something on level " << arg1
                 << ", but this level is empty.");


private:
  BlockInfo block_info_object;

  SmartPointer<const Triangulation<dim, spacedim>, DoFHandler<dim, spacedim>>
    tria;


  hp::FECollection<dim, spacedim> fe_collection;

  std::unique_ptr<::internal::DoFHandlerImplementation::Policy::
                    PolicyBase<dim, spacedim>>
    policy;

  ::internal::DoFHandlerImplementation::NumberCache number_cache;

  std::vector<::internal::DoFHandlerImplementation::NumberCache>
    mg_number_cache;

  class MGVertexDoFs
  {
  public:
    MGVertexDoFs();

    void
    init(const unsigned int coarsest_level,
         const unsigned int finest_level,
         const unsigned int dofs_per_vertex);

    unsigned int
    get_coarsest_level() const;

    unsigned int
    get_finest_level() const;

    types::global_dof_index
    get_index(const unsigned int level,
              const unsigned int dof_number,
              const unsigned int dofs_per_vertex) const;

    void
    set_index(const unsigned int            level,
              const unsigned int            dof_number,
              const unsigned int            dofs_per_vertex,
              const types::global_dof_index index);

  private:
    unsigned int coarsest_level;

    unsigned int finest_level;

    std::unique_ptr<types::global_dof_index[]> indices;
  };

  void
  clear_space();

  void
  clear_mg_space();

  template <int structdim>
  types::global_dof_index
  get_dof_index(const unsigned int obj_level,
                const unsigned int obj_index,
                const unsigned int fe_index,
                const unsigned int local_index) const;

  template <int structdim>
  void
  set_dof_index(const unsigned int            obj_level,
                const unsigned int            obj_index,
                const unsigned int            fe_index,
                const unsigned int            local_index,
                const types::global_dof_index global_index) const;

  std::vector<types::global_dof_index> vertex_dofs;

  std::vector<MGVertexDoFs> mg_vertex_dofs;

  std::vector<
    std::unique_ptr<::internal::DoFHandlerImplementation::DoFLevel<dim>>>
    levels;

  std::vector<
    std::unique_ptr<::internal::DoFHandlerImplementation::DoFLevel<dim>>>
    mg_levels;

  std::unique_ptr<::internal::DoFHandlerImplementation::DoFFaces<dim>>
    faces;

  std::unique_ptr<::internal::DoFHandlerImplementation::DoFFaces<dim>>
    mg_faces;

  // Make accessor objects friends.
  template <int, class, bool>
  friend class DoFAccessor;
  template <class, bool>
  friend class DoFCellAccessor;
  friend struct ::internal::DoFAccessorImplementation::Implementation;
  friend struct ::internal::DoFCellAccessorImplementation::Implementation;

  friend struct ::internal::DoFHandlerImplementation::Implementation;
  friend struct ::internal::DoFHandlerImplementation::Policy::
    Implementation;

  // explicitly check for sensible template arguments, but not on windows
  // because MSVC creates bogus warnings during normal compilation
#ifndef DEAL_II_MSVC
  static_assert(dim <= spacedim,
                "The dimension <dim> of a DoFHandler must be less than or "
                "equal to the space dimension <spacedim> in which it lives.");
#endif
};



#ifndef DOXYGEN

/* ----------------------- Inline functions ----------------------------------
 */


template <int dim, int spacedim>
inline bool
DoFHandler<dim, spacedim>::has_level_dofs() const
{
  return mg_number_cache.size() > 0;
}



template <int dim, int spacedim>
inline bool
DoFHandler<dim, spacedim>::has_active_dofs() const
{
  return number_cache.n_global_dofs > 0;
}



template <int dim, int spacedim>
inline types::global_dof_index
DoFHandler<dim, spacedim>::n_dofs() const
{
  return number_cache.n_global_dofs;
}



template <int dim, int spacedim>
inline types::global_dof_index
DoFHandler<dim, spacedim>::n_dofs(const unsigned int level) const
{
  Assert(has_level_dofs(),
         ExcMessage(
           "n_dofs(level) can only be called after distribute_mg_dofs()"));
  Assert(level < mg_number_cache.size(), ExcInvalidLevel(level));
  return mg_number_cache[level].n_global_dofs;
}



template <int dim, int spacedim>
types::global_dof_index
DoFHandler<dim, spacedim>::n_locally_owned_dofs() const
{
  return number_cache.n_locally_owned_dofs;
}



template <int dim, int spacedim>
const IndexSet &
DoFHandler<dim, spacedim>::locally_owned_dofs() const
{
  return number_cache.locally_owned_dofs;
}



template <int dim, int spacedim>
const IndexSet &
DoFHandler<dim, spacedim>::locally_owned_mg_dofs(const unsigned int level) const
{
  Assert(level < this->get_triangulation().n_global_levels(),
         ExcMessage("The given level index exceeds the number of levels "
                    "present in the triangulation"));
  Assert(
    mg_number_cache.size() == this->get_triangulation().n_global_levels(),
    ExcMessage(
      "The level dofs are not set up properly! Did you call distribute_mg_dofs()?"));
  return mg_number_cache[level].locally_owned_dofs;
}



template <int dim, int spacedim>
const std::vector<types::global_dof_index> &
DoFHandler<dim, spacedim>::n_locally_owned_dofs_per_processor() const
{
  if (number_cache.n_locally_owned_dofs_per_processor.empty() &&
      number_cache.n_global_dofs > 0)
    {
      MPI_Comm comm;

      const parallel::TriangulationBase<dim, spacedim> *tr =
        (dynamic_cast<const parallel::TriangulationBase<dim, spacedim> *>(
          &this->get_triangulation()));
      if (tr != nullptr)
        comm = tr->get_communicator();
      else
        comm = MPI_COMM_SELF;

      const_cast<::internal::DoFHandlerImplementation::NumberCache &>(
        number_cache)
        .n_locally_owned_dofs_per_processor =
        number_cache.get_n_locally_owned_dofs_per_processor(comm);
    }
  return number_cache.n_locally_owned_dofs_per_processor;
}



template <int dim, int spacedim>
const std::vector<IndexSet> &
DoFHandler<dim, spacedim>::locally_owned_dofs_per_processor() const
{
  if (number_cache.locally_owned_dofs_per_processor.empty() &&
      number_cache.n_global_dofs > 0)
    {
      MPI_Comm comm;

      const parallel::TriangulationBase<dim, spacedim> *tr =
        (dynamic_cast<const parallel::TriangulationBase<dim, spacedim> *>(
          &this->get_triangulation()));
      if (tr != nullptr)
        comm = tr->get_communicator();
      else
        comm = MPI_COMM_SELF;

      const_cast<::internal::DoFHandlerImplementation::NumberCache &>(
        number_cache)
        .locally_owned_dofs_per_processor =
        number_cache.get_locally_owned_dofs_per_processor(comm);
    }
  return number_cache.locally_owned_dofs_per_processor;
}



template <int dim, int spacedim>
const std::vector<IndexSet> &
DoFHandler<dim, spacedim>::locally_owned_mg_dofs_per_processor(
  const unsigned int level) const
{
  Assert(level < this->get_triangulation().n_global_levels(),
         ExcMessage("The given level index exceeds the number of levels "
                    "present in the triangulation"));
  Assert(
    mg_number_cache.size() == this->get_triangulation().n_global_levels(),
    ExcMessage(
      "The level dofs are not set up properly! Did you call distribute_mg_dofs()?"));
  if (mg_number_cache[level].locally_owned_dofs_per_processor.empty() &&
      mg_number_cache[level].n_global_dofs > 0)
    {
      MPI_Comm comm;

      const parallel::TriangulationBase<dim, spacedim> *tr =
        (dynamic_cast<const parallel::TriangulationBase<dim, spacedim> *>(
          &this->get_triangulation()));
      if (tr != nullptr)
        comm = tr->get_communicator();
      else
        comm = MPI_COMM_SELF;

      const_cast<::internal::DoFHandlerImplementation::NumberCache &>(
        mg_number_cache[level])
        .locally_owned_dofs_per_processor =
        mg_number_cache[level].get_locally_owned_dofs_per_processor(comm);
    }
  return mg_number_cache[level].locally_owned_dofs_per_processor;
}



template <int dim, int spacedim>
inline const FiniteElement<dim, spacedim> &
DoFHandler<dim, spacedim>::get_fe(const unsigned int index) const
{
  (void)index;
  Assert(index == 0,
         ExcMessage(
           "There is only one FiniteElement stored. The index must be zero!"));
  return get_fe_collection()[0];
}



template <int dim, int spacedim>
inline const hp::FECollection<dim, spacedim> &
DoFHandler<dim, spacedim>::get_fe_collection() const
{
  Assert(
    fe_collection.size() > 0,
    ExcMessage(
      "You are trying to access the DoFHandler's FECollection object before it has been initialized."));
  return fe_collection;
}



template <int dim, int spacedim>
inline const Triangulation<dim, spacedim> &
DoFHandler<dim, spacedim>::get_triangulation() const
{
  Assert(tria != nullptr,
         ExcMessage("This DoFHandler object has not been associated "
                    "with a triangulation."));
  return *tria;
}



template <int dim, int spacedim>
inline const BlockInfo &
DoFHandler<dim, spacedim>::block_info() const
{
  return block_info_object;
}



template <int dim, int spacedim>
template <typename number>
types::global_dof_index
DoFHandler<dim, spacedim>::n_boundary_dofs(
  const std::map<types::boundary_id, const Function<spacedim, number> *>
    &boundary_ids) const
{
  // extract the set of boundary ids and forget about the function object
  // pointers
  std::set<types::boundary_id> boundary_ids_only;
  for (typename std::map<types::boundary_id,
                         const Function<spacedim, number> *>::const_iterator p =
         boundary_ids.begin();
       p != boundary_ids.end();
       ++p)
    boundary_ids_only.insert(p->first);

  // then just hand everything over to the other function that does the work
  return n_boundary_dofs(boundary_ids_only);
}



namespace internal
{
  template <int dim, int spacedim>
  std::string
  policy_to_string(const ::internal::DoFHandlerImplementation::Policy::
                     PolicyBase<dim, spacedim> &policy);
} // namespace internal



template <int dim, int spacedim>
template <class Archive>
void
DoFHandler<dim, spacedim>::save(Archive &ar, const unsigned int) const
{
  ar &block_info_object;
  ar &vertex_dofs;
  ar &number_cache;

  // some versions of gcc have trouble with loading vectors of
  // std::unique_ptr objects because std::unique_ptr does not
  // have a copy constructor. do it one level at a time
  unsigned int n_levels = levels.size();
  ar &         n_levels;
  for (unsigned int i = 0; i < levels.size(); ++i)
    ar &levels[i];

  // boost dereferences a nullptr when serializing a nullptr
  // at least up to 1.65.1. This causes problems with clang-5.
  // Therefore, work around it.
  bool faces_is_nullptr = (faces.get() == nullptr);
  ar & faces_is_nullptr;
  if (!faces_is_nullptr)
    ar &faces;

  // write out the number of triangulation cells and later check during
  // loading that this number is indeed correct; same with something that
  // identifies the FE and the policy
  unsigned int n_cells     = tria->n_cells();
  std::string  fe_name     = this->get_fe(0).get_name();
  std::string  policy_name = internal::policy_to_string(*policy);

  ar &n_cells &fe_name &policy_name;
}



template <int dim, int spacedim>
template <class Archive>
void
DoFHandler<dim, spacedim>::load(Archive &ar, const unsigned int)
{
  ar &block_info_object;
  ar &vertex_dofs;
  ar &number_cache;

  // boost::serialization can restore pointers just fine, but if the
  // pointer object still points to something useful, that object is not
  // destroyed and we end up with a memory leak. consequently, first delete
  // previous content before re-loading stuff
  levels.clear();
  faces.reset();

  // some versions of gcc have trouble with loading vectors of
  // std::unique_ptr objects because std::unique_ptr does not
  // have a copy constructor. do it one level at a time
  unsigned int size;
  ar &         size;
  levels.resize(size);
  for (unsigned int i = 0; i < levels.size(); ++i)
    {
      std::unique_ptr<internal::DoFHandlerImplementation::DoFLevel<dim>> level;
      ar &                                                               level;
      levels[i] = std::move(level);
    }

  // Workaround for nullptr, see in save().
  bool faces_is_nullptr = true;
  ar & faces_is_nullptr;
  if (!faces_is_nullptr)
    ar &faces;

  // these are the checks that correspond to the last block in the save()
  // function
  unsigned int n_cells;
  std::string  fe_name;
  std::string  policy_name;

  ar &n_cells &fe_name &policy_name;

  AssertThrow(n_cells == tria->n_cells(),
              ExcMessage(
                "The object being loaded into does not match the triangulation "
                "that has been stored previously."));
  AssertThrow(
    fe_name == this->get_fe(0).get_name(),
    ExcMessage(
      "The finite element associated with this DoFHandler does not match "
      "the one that was associated with the DoFHandler previously stored."));
  AssertThrow(policy_name == internal::policy_to_string(*policy),
              ExcMessage(
                "The policy currently associated with this DoFHandler (" +
                internal::policy_to_string(*policy) +
                ") does not match the one that was associated with the "
                "DoFHandler previously stored (" +
                policy_name + ")."));
}



template <int dim, int spacedim>
inline types::global_dof_index
DoFHandler<dim, spacedim>::MGVertexDoFs::get_index(
  const unsigned int level,
  const unsigned int dof_number,
  const unsigned int dofs_per_vertex) const
{
  Assert((level >= coarsest_level) && (level <= finest_level),
         ExcInvalidLevel(level));
  return indices[dofs_per_vertex * (level - coarsest_level) + dof_number];
}



template <int dim, int spacedim>
inline void
DoFHandler<dim, spacedim>::MGVertexDoFs::set_index(
  const unsigned int            level,
  const unsigned int            dof_number,
  const unsigned int            dofs_per_vertex,
  const types::global_dof_index index)
{
  Assert((level >= coarsest_level) && (level <= finest_level),
         ExcInvalidLevel(level));
  indices[dofs_per_vertex * (level - coarsest_level) + dof_number] = index;
}


#endif // DOXYGEN

DEAL_II_NAMESPACE_CLOSE

#endif