mg_block_smoother.h

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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 2005 - 2023 by the deal.II authors
//
// This file is part of the deal.II library.
//
// Part of the source code is dual licensed under Apache-2.0 WITH
// LLVM-exception OR LGPL-2.1-or-later. Detailed license information
// governing the source code and code contributions can be found in
// LICENSE.md and CONTRIBUTING.md at the top level directory of deal.II.
//
// ------------------------------------------------------------------------
 
#ifndef dealii_mg_block_smoother_h
#define dealii_mg_block_smoother_h
 
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/mg_level_object.h>
#include <deal.II/base/observer_pointer.h>
 
#include <deal.II/lac/block_vector.h>
#include <deal.II/lac/linear_operator.h>
#include <deal.II/lac/vector_memory.h>
 
#include <deal.II/multigrid/mg_smoother.h>
 
#include <vector>
 
DEAL_II_NAMESPACE_OPEN
 
/*
 * MGSmootherBase is defined in mg_base.h
 */
 
template <typename MatrixType, typename RelaxationType, typename number>
class MGSmootherBlock : public MGSmoother<BlockVector<number>>
{
public:
  MGSmootherBlock(const unsigned int steps     = 1,
                  const bool         variable  = false,
                  const bool         symmetric = false,
                  const bool         transpose = false,
                  const bool         reverse   = false);
 
  template <typename MGMatrixType, typename MGRelaxationType>
  void
  initialize(const MGMatrixType &matrices, const MGRelaxationType &smoothers);
 
  void
  clear();
 
  void
  set_reverse(const bool);
 
  virtual void
  smooth(const unsigned int         level,
         BlockVector<number>       &u,
         const BlockVector<number> &rhs) const;
 
  std::size_t
  memory_consumption() const;
 
private:
  MGLevelObject<LinearOperator<BlockVector<number>>> matrices;
 
  MGLevelObject<LinearOperator<BlockVector<number>>> smoothers;
 
  bool reverse;
 
  ObserverPointer<VectorMemory<BlockVector<number>>,
                  MGSmootherBlock<MatrixType, RelaxationType, number>>
    mem;
};
 
//---------------------------------------------------------------------------
 
#ifndef DOXYGEN
 
template <typename MatrixType, typename RelaxationType, typename number>
inline MGSmootherBlock<MatrixType, RelaxationType, number>::MGSmootherBlock(
  const unsigned int steps,
  const bool         variable,
  const bool         symmetric,
  const bool         transpose,
  const bool         reverse)
  : MGSmoother<BlockVector<number>>(steps, variable, symmetric, transpose)
  , reverse(reverse)
  , mem(&this->vector_memory)
{}
 
 
template <typename MatrixType, typename RelaxationType, typename number>
inline void
MGSmootherBlock<MatrixType, RelaxationType, number>::clear()
{
  unsigned int i = matrices.min_level(), max_level = matrices.max_level();
  for (; i <= max_level; ++i)
    {
      smoothers[i] = LinearOperator<BlockVector<number>>();
      matrices[i]  = LinearOperator<BlockVector<number>>();
    }
}
 
 
template <typename MatrixType, typename RelaxationType, typename number>
template <typename MGMatrixType, typename MGRelaxationType>
inline void
MGSmootherBlock<MatrixType, RelaxationType, number>::initialize(
  const MGMatrixType     &m,
  const MGRelaxationType &s)
{
  const unsigned int min = m.min_level();
  const unsigned int max = m.max_level();
 
  matrices.resize(min, max);
  smoothers.resize(min, max);
 
  for (unsigned int i = min; i <= max; ++i)
    {
      // Workaround: Unfortunately, not every "m[i]" object has a
      // rich enough interface to populate reinit_(domain|range)_vector.
      // Thus, apply an empty LinearOperator exemplar.
      matrices[i] = linear_operator<BlockVector<number>>(
        LinearOperator<BlockVector<number>>(), m[i]);
      smoothers[i] = linear_operator<BlockVector<number>>(matrices[i], s[i]);
    }
}
 
 
template <typename MatrixType, typename RelaxationType, typename number>
inline void
MGSmootherBlock<MatrixType, RelaxationType, number>::set_reverse(
  const bool flag)
{
  reverse = flag;
}
 
 
template <typename MatrixType, typename RelaxationType, typename number>
inline std::size_t
MGSmootherBlock<MatrixType, RelaxationType, number>::memory_consumption() const
{
  return sizeof(*this) + matrices.memory_consumption() +
         smoothers.memory_consumption() +
         this->vector_memory.memory_consumption();
}
 
 
template <typename MatrixType, typename RelaxationType, typename number>
inline void
MGSmootherBlock<MatrixType, RelaxationType, number>::smooth(
  const unsigned int         level,
  BlockVector<number>       &u,
  const BlockVector<number> &rhs) const
{
  LogStream::Prefix prefix("Smooth");
 
  unsigned int maxlevel = matrices.max_level();
  unsigned int steps2   = this->steps;
 
  if (this->variable)
    steps2 *= (1 << (maxlevel - level));
 
  typename VectorMemory<BlockVector<number>>::Pointer r(*this->mem);
  typename VectorMemory<BlockVector<number>>::Pointer d(*this->mem);
  r->reinit(u);
  d->reinit(u);
 
  bool T = this->transpose;
  if (this->symmetric && (steps2 % 2 == 0))
    T = false;
 
  for (unsigned int i = 0; i < steps2; ++i)
    {
      if (T)
        {
          matrices[level].vmult(*r, u);
          r->sadd(-1., 1., rhs);
          smoothers[level].Tvmult(*d, *r);
        }
      else
        {
          matrices[level].vmult(*r, u);
          r->sadd(-1., 1., rhs);
          smoothers[level].vmult(*d, *r);
        }
      u += *d;
      if (this->symmetric)
        T = !T;
    }
}
 
#endif // DOXYGEN
 
DEAL_II_NAMESPACE_CLOSE
 
#endif