solver.h

// ---------------------------------------------------------------------
//
// Copyright (C) 1998 - 2018 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_solver_h
#define dealii_solver_h

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

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

#include <deal.II/lac/solver_control.h>
#include <deal.II/lac/vector_memory.h>

// Ignore deprecation warnings for auto_ptr.
#include <boost/signals2.hpp>

DEAL_II_NAMESPACE_OPEN

template <typename number>
class Vector;

template <class VectorType = Vector<double>>
class Solver : public Subscriptor
{
public:
  using vector_type = VectorType;

  Solver(SolverControl &           solver_control,
         VectorMemory<VectorType> &vector_memory);

  Solver(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 ------------------------*/


template <class VectorType>
inline SolverControl::State
Solver<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 <class VectorType>
template <typename Iterator>
inline SolverControl::State
Solver<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 <class VectorType>
inline Solver<VectorType>::Solver(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(std::bind(&SolverControl::check,
                    std::ref(solver_control),
                    std::placeholders::_1,
                    std::placeholders::_2));
}



template <class VectorType>
inline Solver<VectorType>::Solver(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(std::bind(&SolverControl::check,
                    std::ref(solver_control),
                    std::placeholders::_1,
                    std::placeholders::_2));
}



template <class VectorType>
inline boost::signals2::connection
Solver<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);
}



DEAL_II_NAMESPACE_CLOSE

#endif