solver.h

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// ------------------------------------------------------------------------
//
// SPDX-License-Identifier: LGPL-2.1-or-later
// Copyright (C) 1998 - 2024 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_solver_h
#define dealii_solver_h
 
#include <deal.II/base/config.h>
 
#include <deal.II/base/subscriptor.h>
#include <deal.II/base/template_constraints.h>
 
#include <deal.II/lac/solver_control.h>
#include <deal.II/lac/vector_memory.h>
 
#include <boost/signals2.hpp>
 
DEAL_II_NAMESPACE_OPEN
 
// Forward declaration
#ifndef DOXYGEN
template <typename number>
class Vector;
#endif
 
template <typename VectorType = Vector<double>>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
class SolverBase : public Subscriptor
{
public:
  using vector_type = VectorType;
 
  SolverBase(SolverControl            &solver_control,
             VectorMemory<VectorType> &vector_memory);
 
  SolverBase(SolverControl &solver_control);
 
  boost::signals2::connection
  connect(
    const std::function<SolverControl::State(const unsigned int iteration,
                                             const double       check_value,
                                             const VectorType &current_iterate)>
      &slot);
 
 
 
protected:
  mutable GrowingVectorMemory<VectorType> static_vector_memory;
 
  VectorMemory<VectorType> &memory;
 
private:
  struct StateCombiner
  {
    using result_type = SolverControl::State;
 
    SolverControl::State
    operator()(const SolverControl::State state1,
               const SolverControl::State state2) const;
 
    template <typename Iterator>
    SolverControl::State
    operator()(const Iterator begin, const Iterator end) const;
  };
 
protected:
  boost::signals2::signal<
    SolverControl::State(const unsigned int iteration,
                         const double       check_value,
                         const VectorType  &current_iterate),
    StateCombiner>
    iteration_status;
};
 
 
 
/*-------------------------------- Inline functions ------------------------*/
#ifndef DOXYGEN
 
template <typename VectorType>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
inline SolverControl::State SolverBase<VectorType>::StateCombiner::operator()(
  const SolverControl::State state1,
  const SolverControl::State state2) const
{
  if ((state1 == SolverControl::failure) || (state2 == SolverControl::failure))
    return SolverControl::failure;
  else if ((state1 == SolverControl::iterate) ||
           (state2 == SolverControl::iterate))
    return SolverControl::iterate;
  else
    return SolverControl::success;
}
 
 
template <typename VectorType>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
template <typename Iterator>
inline SolverControl::State
  SolverBase<VectorType>::StateCombiner::operator()(const Iterator begin,
                                                    const Iterator end) const
{
  Assert(begin != end,
         ExcMessage("You can't combine iterator states if no state is given."));
 
  // combine the first with all of the following states
  SolverControl::State state = *begin;
  Iterator             p     = begin;
  ++p;
  for (; p != end; ++p)
    state = this->operator()(state, *p);
 
  return state;
}
 
 
template <typename VectorType>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
inline SolverBase<VectorType>::SolverBase(
  SolverControl            &solver_control,
  VectorMemory<VectorType> &vector_memory)
  : memory(vector_memory)
{
  // connect the solver control object to the signal. SolverControl::check
  // only takes two arguments, the iteration and the check_value, and so
  // we simply ignore the third argument that is passed in whenever the
  // signal is executed
  connect([&solver_control](const unsigned int iteration,
                            const double       check_value,
                            const VectorType &) {
    return solver_control.check(iteration, check_value);
  });
}
 
 
 
template <typename VectorType>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
inline SolverBase<VectorType>::SolverBase(SolverControl &solver_control)
  : // use the static memory object this class owns
  memory(static_vector_memory)
{
  // connect the solver control object to the signal. SolverControl::check
  // only takes two arguments, the iteration and the check_value, and so
  // we simply ignore the third argument that is passed in whenever the
  // signal is executed
  connect([&solver_control](const unsigned int iteration,
                            const double       check_value,
                            const VectorType &) {
    return solver_control.check(iteration, check_value);
  });
}
 
 
 
template <typename VectorType>
DEAL_II_CXX20_REQUIRES(concepts::is_vector_space_vector<VectorType>)
inline boost::signals2::connection SolverBase<VectorType>::connect(
  const std::function<SolverControl::State(const unsigned int iteration,
                                           const double       check_value,
                                           const VectorType  &current_iterate)>
    &slot)
{
  return iteration_status.connect(slot);
}
 
#endif
 
DEAL_II_NAMESPACE_CLOSE
 
#endif