multigrid.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 1999 - 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_multigrid_h
#define dealii_multigrid_h


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

#include <deal.II/base/mg_level_object.h>
#include <deal.II/base/smartpointer.h>
#include <deal.II/base/subscriptor.h>

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

#include <deal.II/dofs/dof_handler.h>

#include <deal.II/lac/sparse_matrix.h>
#include <deal.II/lac/vector.h>

#include <deal.II/multigrid/mg_base.h>

#include <vector>

DEAL_II_NAMESPACE_OPEN


namespace mg
{
  struct Signals
  {
    boost::signals2::signal<void(const bool before)> transfer_to_mg;

    boost::signals2::signal<void(const bool before)> transfer_to_global;

    boost::signals2::signal<void(const bool before, const unsigned int level)>
      coarse_solve;

    boost::signals2::signal<void(const bool before, const unsigned int level)>
      restriction;

    boost::signals2::signal<void(const bool before, const unsigned int level)>
      prolongation;

    boost::signals2::signal<void(const bool before, const unsigned int level)>
      pre_smoother_step;

    boost::signals2::signal<void(const bool before, const unsigned int level)>
      post_smoother_step;
  };
} // namespace mg

template <typename VectorType>
class Multigrid : public Subscriptor
{
public:
  enum Cycle
  {
    v_cycle,
    w_cycle,
    f_cycle
  };

  using vector_type       = VectorType;
  using const_vector_type = const VectorType;

  Multigrid(const MGMatrixBase<VectorType> &    matrix,
            const MGCoarseGridBase<VectorType> &coarse,
            const MGTransferBase<VectorType> &  transfer,
            const MGSmootherBase<VectorType> &  pre_smooth,
            const MGSmootherBase<VectorType> &  post_smooth,
            const unsigned int                  minlevel = 0,
            const unsigned int maxlevel = numbers::invalid_unsigned_int,
            Cycle              cycle    = v_cycle);

  void
  reinit(const unsigned int minlevel, const unsigned int maxlevel);

  void
  cycle();

  void
  vcycle();

  void
  set_edge_matrices(const MGMatrixBase<VectorType> &edge_out,
                    const MGMatrixBase<VectorType> &edge_in);

  void
  set_edge_flux_matrices(const MGMatrixBase<VectorType> &edge_down,
                         const MGMatrixBase<VectorType> &edge_up);

  unsigned int
  get_maxlevel() const;

  unsigned int
  get_minlevel() const;

  void
  set_maxlevel(const unsigned int);

  void
  set_minlevel(const unsigned int level, bool relative = false);

  void set_cycle(Cycle);

  boost::signals2::connection
  connect_coarse_solve(
    const std::function<void(const bool, const unsigned int)> &slot);

  boost::signals2::connection
  connect_restriction(
    const std::function<void(const bool, const unsigned int)> &slot);

  boost::signals2::connection
  connect_prolongation(
    const std::function<void(const bool, const unsigned int)> &slot);

  boost::signals2::connection
  connect_pre_smoother_step(
    const std::function<void(const bool, const unsigned int)> &slot);

  boost::signals2::connection
  connect_post_smoother_step(
    const std::function<void(const bool, const unsigned int)> &slot);

private:
  mg::Signals signals;

  void
  level_v_step(const unsigned int level);

  void
  level_step(const unsigned int level, Cycle cycle);

  Cycle cycle_type;

  unsigned int minlevel;

  unsigned int maxlevel;

public:
  MGLevelObject<VectorType> defect;

  MGLevelObject<VectorType> solution;

private:
  MGLevelObject<VectorType> t;

  MGLevelObject<VectorType> defect2;


  SmartPointer<const MGMatrixBase<VectorType>, Multigrid<VectorType>> matrix;

  SmartPointer<const MGCoarseGridBase<VectorType>, Multigrid<VectorType>>
    coarse;

  SmartPointer<const MGTransferBase<VectorType>, Multigrid<VectorType>>
    transfer;

  SmartPointer<const MGSmootherBase<VectorType>, Multigrid<VectorType>>
    pre_smooth;

  SmartPointer<const MGSmootherBase<VectorType>, Multigrid<VectorType>>
    post_smooth;

  SmartPointer<const MGMatrixBase<VectorType>> edge_out;

  SmartPointer<const MGMatrixBase<VectorType>> edge_in;

  SmartPointer<const MGMatrixBase<VectorType>, Multigrid<VectorType>> edge_down;

  SmartPointer<const MGMatrixBase<VectorType>, Multigrid<VectorType>> edge_up;

  template <int dim, class OtherVectorType, class TRANSFER>
  friend class PreconditionMG;
};


template <int dim, typename VectorType, class TRANSFER>
class PreconditionMG : public Subscriptor
{
public:
  PreconditionMG(const DoFHandler<dim> &dof_handler,
                 Multigrid<VectorType> &mg,
                 const TRANSFER &       transfer);

  PreconditionMG(const std::vector<const DoFHandler<dim> *> &dof_handler,
                 Multigrid<VectorType> &                     mg,
                 const TRANSFER &                            transfer);

  bool
  empty() const;

  template <class OtherVectorType>
  void
  vmult(OtherVectorType &dst, const OtherVectorType &src) const;

  template <class OtherVectorType>
  void
  vmult_add(OtherVectorType &dst, const OtherVectorType &src) const;

  template <class OtherVectorType>
  void
  Tvmult(OtherVectorType &dst, const OtherVectorType &src) const;

  template <class OtherVectorType>
  void
  Tvmult_add(OtherVectorType &dst, const OtherVectorType &src) const;

  IndexSet
  locally_owned_range_indices(const unsigned int block = 0) const;

  IndexSet
  locally_owned_domain_indices(const unsigned int block = 0) const;

  const MPI_Comm &
  get_mpi_communicator() const;

  boost::signals2::connection
  connect_transfer_to_mg(const std::function<void(bool)> &slot);

  boost::signals2::connection
  connect_transfer_to_global(const std::function<void(bool)> &slot);

private:
  std::vector<SmartPointer<const DoFHandler<dim>,
                           PreconditionMG<dim, VectorType, TRANSFER>>>
    dof_handler_vector;

  std::vector<const DoFHandler<dim> *> dof_handler_vector_raw;

  SmartPointer<Multigrid<VectorType>, PreconditionMG<dim, VectorType, TRANSFER>>
    multigrid;

  SmartPointer<const TRANSFER, PreconditionMG<dim, VectorType, TRANSFER>>
    transfer;

  const bool uses_dof_handler_vector;

  mg::Signals signals;
};

#ifndef DOXYGEN
/* --------------------------- inline functions --------------------- */


template <typename VectorType>
Multigrid<VectorType>::Multigrid(const MGMatrixBase<VectorType> &    matrix,
                                 const MGCoarseGridBase<VectorType> &coarse,
                                 const MGTransferBase<VectorType> &  transfer,
                                 const MGSmootherBase<VectorType> &  pre_smooth,
                                 const MGSmootherBase<VectorType> &post_smooth,
                                 const unsigned int                min_level,
                                 const unsigned int                max_level,
                                 Cycle                             cycle)
  : cycle_type(cycle)
  , matrix(&matrix, typeid(*this).name())
  , coarse(&coarse, typeid(*this).name())
  , transfer(&transfer, typeid(*this).name())
  , pre_smooth(&pre_smooth, typeid(*this).name())
  , post_smooth(&post_smooth, typeid(*this).name())
  , edge_out(nullptr, typeid(*this).name())
  , edge_in(nullptr, typeid(*this).name())
  , edge_down(nullptr, typeid(*this).name())
  , edge_up(nullptr, typeid(*this).name())
{
  if (max_level == numbers::invalid_unsigned_int)
    maxlevel = matrix.get_maxlevel();
  else
    maxlevel = max_level;
  reinit(min_level, maxlevel);
}



template <typename VectorType>
inline unsigned int
Multigrid<VectorType>::get_maxlevel() const
{
  return maxlevel;
}



template <typename VectorType>
inline unsigned int
Multigrid<VectorType>::get_minlevel() const
{
  return minlevel;
}


/* --------------------------- inline functions --------------------- */


namespace internal
{
  namespace PreconditionMGImplementation
  {
    template <int dim,
              typename VectorType,
              class TRANSFER,
              typename OtherVectorType>
    typename std::enable_if<TRANSFER::supports_dof_handler_vector>::type
    vmult(
      const std::vector<const ::DoFHandler<dim> *> &dof_handler_vector,
      ::Multigrid<VectorType> &                     multigrid,
      const TRANSFER &                                    transfer,
      OtherVectorType &                                   dst,
      const OtherVectorType &                             src,
      const bool                          uses_dof_handler_vector,
      const typename ::mg::Signals &signals,
      int)
    {
      signals.transfer_to_mg(true);
      if (uses_dof_handler_vector)
        transfer.copy_to_mg(dof_handler_vector, multigrid.defect, src);
      else
        transfer.copy_to_mg(*dof_handler_vector[0], multigrid.defect, src);
      signals.transfer_to_mg(false);

      multigrid.cycle();

      signals.transfer_to_global(true);
      if (uses_dof_handler_vector)
        transfer.copy_from_mg(dof_handler_vector, dst, multigrid.solution);
      else
        transfer.copy_from_mg(*dof_handler_vector[0], dst, multigrid.solution);
      signals.transfer_to_global(false);
    }

    template <int dim,
              typename VectorType,
              class TRANSFER,
              typename OtherVectorType>
    void
    vmult(
      const std::vector<const ::DoFHandler<dim> *> &dof_handler_vector,
      ::Multigrid<VectorType> &                     multigrid,
      const TRANSFER &                                    transfer,
      OtherVectorType &                                   dst,
      const OtherVectorType &                             src,
      const bool                          uses_dof_handler_vector,
      const typename ::mg::Signals &signals,
      ...)
    {
      (void)uses_dof_handler_vector;
      Assert(!uses_dof_handler_vector, ExcInternalError());

      signals.transfer_to_mg(true);
      transfer.copy_to_mg(*dof_handler_vector[0], multigrid.defect, src);
      signals.transfer_to_mg(false);

      multigrid.cycle();

      signals.transfer_to_global(true);
      transfer.copy_from_mg(*dof_handler_vector[0], dst, multigrid.solution);
      signals.transfer_to_global(false);
    }

    template <int dim,
              typename VectorType,
              class TRANSFER,
              typename OtherVectorType>
    typename std::enable_if<TRANSFER::supports_dof_handler_vector>::type
    vmult_add(
      const std::vector<const ::DoFHandler<dim> *> &dof_handler_vector,
      ::Multigrid<VectorType> &                     multigrid,
      const TRANSFER &                                    transfer,
      OtherVectorType &                                   dst,
      const OtherVectorType &                             src,
      const bool                          uses_dof_handler_vector,
      const typename ::mg::Signals &signals,
      int)
    {
      signals.transfer_to_mg(true);
      if (uses_dof_handler_vector)
        transfer.copy_to_mg(dof_handler_vector, multigrid.defect, src);
      else
        transfer.copy_to_mg(*dof_handler_vector[0], multigrid.defect, src);
      signals.transfer_to_mg(false);

      multigrid.cycle();

      signals.transfer_to_global(true);
      if (uses_dof_handler_vector)
        transfer.copy_from_mg_add(dof_handler_vector, dst, multigrid.solution);
      else
        transfer.copy_from_mg_add(*dof_handler_vector[0],
                                  dst,
                                  multigrid.solution);
      signals.transfer_to_global(false);
    }

    template <int dim,
              typename VectorType,
              class TRANSFER,
              typename OtherVectorType>
    void
    vmult_add(
      const std::vector<const ::DoFHandler<dim> *> &dof_handler_vector,
      ::Multigrid<VectorType> &                     multigrid,
      const TRANSFER &                                    transfer,
      OtherVectorType &                                   dst,
      const OtherVectorType &                             src,
      const bool                          uses_dof_handler_vector,
      const typename ::mg::Signals &signals,
      ...)
    {
      (void)uses_dof_handler_vector;
      Assert(!uses_dof_handler_vector, ExcInternalError());

      signals.transfer_to_mg(true);
      transfer.copy_to_mg(*dof_handler_vector[0], multigrid.defect, src);
      signals.transfer_to_mg(false);

      multigrid.cycle();

      signals.transfer_to_global(true);
      transfer.copy_from_mg_add(*dof_handler_vector[0],
                                dst,
                                multigrid.solution);
      signals.transfer_to_global(false);
    }
  } // namespace PreconditionMGImplementation
} // namespace internal

template <int dim, typename VectorType, class TRANSFER>
PreconditionMG<dim, VectorType, TRANSFER>::PreconditionMG(
  const DoFHandler<dim> &dof_handler,
  Multigrid<VectorType> &mg,
  const TRANSFER &       transfer)
  : dof_handler_vector(1, &dof_handler)
  , dof_handler_vector_raw(1, &dof_handler)
  , multigrid(&mg)
  , transfer(&transfer)
  , uses_dof_handler_vector(false)
{}

template <int dim, typename VectorType, class TRANSFER>
PreconditionMG<dim, VectorType, TRANSFER>::PreconditionMG(
  const std::vector<const DoFHandler<dim> *> &dof_handler,
  Multigrid<VectorType> &                     mg,
  const TRANSFER &                            transfer)
  : dof_handler_vector(dof_handler.size())
  , dof_handler_vector_raw(dof_handler.size())
  , multigrid(&mg)
  , transfer(&transfer)
  , uses_dof_handler_vector(true)
{
  for (unsigned int i = 0; i < dof_handler.size(); ++i)
    {
      dof_handler_vector[i]     = dof_handler[i];
      dof_handler_vector_raw[i] = dof_handler[i];
    }
}

template <int dim, typename VectorType, class TRANSFER>
inline bool
PreconditionMG<dim, VectorType, TRANSFER>::empty() const
{
  return false;
}

template <int dim, typename VectorType, class TRANSFER>
template <class OtherVectorType>
void
PreconditionMG<dim, VectorType, TRANSFER>::vmult(
  OtherVectorType &      dst,
  const OtherVectorType &src) const
{
  internal::PreconditionMGImplementation::vmult(dof_handler_vector_raw,
                                                *multigrid,
                                                *transfer,
                                                dst,
                                                src,
                                                uses_dof_handler_vector,
                                                this->signals,
                                                0);
}


template <int dim, typename VectorType, class TRANSFER>
IndexSet
PreconditionMG<dim, VectorType, TRANSFER>::locally_owned_range_indices(
  const unsigned int block) const
{
  AssertIndexRange(block, dof_handler_vector.size());
  return dof_handler_vector[block]->locally_owned_dofs();
}


template <int dim, typename VectorType, class TRANSFER>
IndexSet
PreconditionMG<dim, VectorType, TRANSFER>::locally_owned_domain_indices(
  const unsigned int block) const
{
  AssertIndexRange(block, dof_handler_vector.size());
  return dof_handler_vector[block]->locally_owned_dofs();
}



template <int dim, typename VectorType, class TRANSFER>
const MPI_Comm &
PreconditionMG<dim, VectorType, TRANSFER>::get_mpi_communicator() const
{
  // currently parallel GMG works with parallel triangulations only,
  // so it should be a safe bet to use it to query MPI communicator:
  const Triangulation<dim> &tria = dof_handler_vector[0]->get_triangulation();
  const parallel::TriangulationBase<dim> *ptria =
    dynamic_cast<const parallel::TriangulationBase<dim> *>(&tria);
  Assert(ptria != nullptr, ExcInternalError());
  return ptria->get_communicator();
}



template <int dim, typename VectorType, class TRANSFER>
boost::signals2::connection
PreconditionMG<dim, VectorType, TRANSFER>::connect_transfer_to_mg(
  const std::function<void(bool)> &slot)
{
  return this->signals.transfer_to_mg.connect(slot);
}



template <int dim, typename VectorType, class TRANSFER>
boost::signals2::connection
PreconditionMG<dim, VectorType, TRANSFER>::connect_transfer_to_global(
  const std::function<void(bool)> &slot)
{
  return this->signals.transfer_to_global.connect(slot);
}



template <int dim, typename VectorType, class TRANSFER>
template <class OtherVectorType>
void
PreconditionMG<dim, VectorType, TRANSFER>::vmult_add(
  OtherVectorType &      dst,
  const OtherVectorType &src) const
{
  internal::PreconditionMGImplementation::vmult_add(dof_handler_vector_raw,
                                                    *multigrid,
                                                    *transfer,
                                                    dst,
                                                    src,
                                                    uses_dof_handler_vector,
                                                    this->signals,
                                                    0);
}


template <int dim, typename VectorType, class TRANSFER>
template <class OtherVectorType>
void
PreconditionMG<dim, VectorType, TRANSFER>::Tvmult(OtherVectorType &,
                                                  const OtherVectorType &) const
{
  Assert(false, ExcNotImplemented());
}


template <int dim, typename VectorType, class TRANSFER>
template <class OtherVectorType>
void
PreconditionMG<dim, VectorType, TRANSFER>::Tvmult_add(
  OtherVectorType &,
  const OtherVectorType &) const
{
  Assert(false, ExcNotImplemented());
}

#endif // DOXYGEN

DEAL_II_NAMESPACE_CLOSE

#endif