mg_coarse.h

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// ---------------------------------------------------------------------
//
// Copyright (C) 2002 - 2021 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_mg_coarse_h
#define dealii_mg_coarse_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/lac/full_matrix.h>
#include <deal.II/lac/householder.h>
#include <deal.II/lac/linear_operator.h>
 
#include <deal.II/multigrid/mg_base.h>
 
DEAL_II_NAMESPACE_OPEN
 
 
template <class VectorType = Vector<double>>
class MGCoarseGridApplySmoother : public MGCoarseGridBase<VectorType>
{
public:
  MGCoarseGridApplySmoother();
 
  MGCoarseGridApplySmoother(const MGSmootherBase<VectorType> &coarse_smooth);
 
  void
  clear();
 
  void
  initialize(const MGSmootherBase<VectorType> &coarse_smooth);
 
  void
  operator()(const unsigned int level,
             VectorType &       dst,
             const VectorType & src) const override;
 
private:
  SmartPointer<const MGSmootherBase<VectorType>,
               MGCoarseGridApplySmoother<VectorType>>
    coarse_smooth;
};
 
 
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
class MGCoarseGridIterativeSolver : public MGCoarseGridBase<VectorType>
{
public:
  MGCoarseGridIterativeSolver();
 
  MGCoarseGridIterativeSolver(SolverType &              solver,
                              const MatrixType &        matrix,
                              const PreconditionerType &precondition);
 
  void
  initialize(SolverType &              solver,
             const MatrixType &        matrix,
             const PreconditionerType &precondition);
 
  void
  clear();
 
  virtual void
  operator()(const unsigned int level,
             VectorType &       dst,
             const VectorType & src) const override;
 
private:
  SmartPointer<SolverType,
               MGCoarseGridIterativeSolver<VectorType,
                                           SolverType,
                                           MatrixType,
                                           PreconditionerType>>
    solver;
 
  SmartPointer<const MatrixType,
               MGCoarseGridIterativeSolver<VectorType,
                                           SolverType,
                                           MatrixType,
                                           PreconditionerType>>
    matrix;
 
  SmartPointer<const PreconditionerType,
               MGCoarseGridIterativeSolver<VectorType,
                                           SolverType,
                                           MatrixType,
                                           PreconditionerType>>
    preconditioner;
};
 
 
 
template <typename number = double, class VectorType = Vector<number>>
class MGCoarseGridHouseholder : public MGCoarseGridBase<VectorType>
{
public:
  MGCoarseGridHouseholder(const FullMatrix<number> *A = nullptr);
 
  void
  initialize(const FullMatrix<number> &A);
 
  void
  operator()(const unsigned int level,
             VectorType &       dst,
             const VectorType & src) const override;
 
private:
  Householder<number> householder;
};
 
template <typename number = double, class VectorType = Vector<number>>
class MGCoarseGridSVD : public MGCoarseGridBase<VectorType>
{
public:
  MGCoarseGridSVD() = default;
 
  void
  initialize(const FullMatrix<number> &A, const double threshold = 0);
 
  void
  operator()(const unsigned int level,
             VectorType &       dst,
             const VectorType & src) const;
 
  void
  log() const;
 
private:
  LAPACKFullMatrix<number> matrix;
};
 
#ifndef DOXYGEN
/* ------------------ Functions for MGCoarseGridApplySmoother -----------*/
template <class VectorType>
MGCoarseGridApplySmoother<VectorType>::MGCoarseGridApplySmoother()
  : coarse_smooth(nullptr)
{}
 
template <class VectorType>
MGCoarseGridApplySmoother<VectorType>::MGCoarseGridApplySmoother(
  const MGSmootherBase<VectorType> &coarse_smooth)
  : coarse_smooth(nullptr)
{
  initialize(coarse_smooth);
}
 
 
template <class VectorType>
void
MGCoarseGridApplySmoother<VectorType>::initialize(
  const MGSmootherBase<VectorType> &coarse_smooth_)
{
  coarse_smooth =
    SmartPointer<const MGSmootherBase<VectorType>,
                 MGCoarseGridApplySmoother<VectorType>>(&coarse_smooth_,
                                                        typeid(*this).name());
}
 
 
template <class VectorType>
void
MGCoarseGridApplySmoother<VectorType>::clear()
{
  coarse_smooth = nullptr;
}
 
 
template <class VectorType>
void
MGCoarseGridApplySmoother<VectorType>::operator()(const unsigned int level,
                                                  VectorType &       dst,
                                                  const VectorType & src) const
{
  coarse_smooth->apply(level, dst, src);
}
 
/* ------------------ Functions for MGCoarseGridIterativeSolver ------------ */
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
MGCoarseGridIterativeSolver<VectorType,
                            SolverType,
                            MatrixType,
                            PreconditionerType>::MGCoarseGridIterativeSolver()
  : solver(0, typeid(*this).name())
  , matrix(0, typeid(*this).name())
  , preconditioner(0, typeid(*this).name())
{}
 
 
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
MGCoarseGridIterativeSolver<VectorType,
                            SolverType,
                            MatrixType,
                            PreconditionerType>::
  MGCoarseGridIterativeSolver(SolverType &              solver,
                              const MatrixType &        matrix,
                              const PreconditionerType &preconditioner)
  : solver(&solver, typeid(*this).name())
  , matrix(&matrix, typeid(*this).name())
  , preconditioner(&preconditioner, typeid(*this).name())
{}
 
 
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
void
MGCoarseGridIterativeSolver<
  VectorType,
  SolverType,
  MatrixType,
  PreconditionerType>::initialize(SolverType &              solver_,
                                  const MatrixType &        matrix_,
                                  const PreconditionerType &preconditioner_)
{
  solver         = &solver_;
  matrix         = &matrix_;
  preconditioner = &preconditioner_;
}
 
 
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
void
MGCoarseGridIterativeSolver<VectorType,
                            SolverType,
                            MatrixType,
                            PreconditionerType>::clear()
{
  solver         = 0;
  matrix         = 0;
  preconditioner = 0;
}
 
 
 
namespace internal
{
  namespace MGCoarseGridIterativeSolver
  {
    template <
      class VectorType,
      class SolverType,
      class MatrixType,
      class PreconditionerType,
      typename std::enable_if<
        std::is_same<VectorType, typename SolverType::vector_type>::value,
        VectorType>::type * = nullptr>
    void
    solve(SolverType &              solver,
          const MatrixType &        matrix,
          const PreconditionerType &preconditioner,
          VectorType &              dst,
          const VectorType &        src)
    {
      solver.solve(matrix, dst, src, preconditioner);
    }
 
    template <
      class VectorType,
      class SolverType,
      class MatrixType,
      class PreconditionerType,
      typename std::enable_if<
        !std::is_same<VectorType, typename SolverType::vector_type>::value,
        VectorType>::type * = nullptr>
    void
    solve(SolverType &              solver,
          const MatrixType &        matrix,
          const PreconditionerType &preconditioner,
          VectorType &              dst,
          const VectorType &        src)
    {
      typename SolverType::vector_type src_;
      typename SolverType::vector_type dst_;
 
      src_ = src;
      dst_ = dst;
 
      solver.solve(matrix, dst_, src_, preconditioner);
 
      dst = dst_;
    }
  } // namespace MGCoarseGridIterativeSolver
} // namespace internal
 
 
 
template <class VectorType,
          class SolverType,
          class MatrixType,
          class PreconditionerType>
void
                       MGCoarseGridIterativeSolver<
                         VectorType,
                         SolverType,
                         MatrixType,
                         PreconditionerType>::operator()(const unsigned int /*level*/,
                                  VectorType &      dst,
                                  const VectorType &src) const
{
  Assert(solver != nullptr, ExcNotInitialized());
  Assert(matrix != nullptr, ExcNotInitialized());
  Assert(preconditioner != nullptr, ExcNotInitialized());
 
  dst = 0;
  internal::MGCoarseGridIterativeSolver::solve(
    *solver, *matrix, *preconditioner, dst, src);
}
 
 
 
/* ------------------ Functions for MGCoarseGridHouseholder ------------ */
 
template <typename number, class VectorType>
MGCoarseGridHouseholder<number, VectorType>::MGCoarseGridHouseholder(
  const FullMatrix<number> *A)
{
  if (A != nullptr)
    householder.initialize(*A);
}
 
 
 
template <typename number, class VectorType>
void
MGCoarseGridHouseholder<number, VectorType>::initialize(
  const FullMatrix<number> &A)
{
  householder.initialize(A);
}
 
 
 
template <typename number, class VectorType>
void
MGCoarseGridHouseholder<number, VectorType>::operator()(
  const unsigned int /*level*/,
  VectorType &      dst,
  const VectorType &src) const
{
  householder.least_squares(dst, src);
}
 
//---------------------------------------------------------------------------
 
 
 
template <typename number, class VectorType>
void
MGCoarseGridSVD<number, VectorType>::initialize(const FullMatrix<number> &A,
                                                double threshold)
{
  matrix.reinit(A.n_rows(), A.n_cols());
  matrix = A;
  matrix.compute_inverse_svd(threshold);
}
 
 
template <typename number, class VectorType>
void
MGCoarseGridSVD<number, VectorType>::operator()(const unsigned int /*level*/,
                                                VectorType &      dst,
                                                const VectorType &src) const
{
  matrix.vmult(dst, src);
}
 
 
template <typename number, class VectorType>
void
MGCoarseGridSVD<number, VectorType>::log() const
{
  const unsigned int n = std::min(matrix.n_rows(), matrix.n_cols());
 
  for (unsigned int i = 0; i < n; ++i)
    deallog << ' ' << matrix.singular_value(i);
  deallog << std::endl;
}
 
 
#endif // DOXYGEN
 
DEAL_II_NAMESPACE_CLOSE
 
#endif