text: /***********************************************************************
  This file is part of the librjmcmc project source files.
  
  Copyright : Institut Geographique National (2008-2012)
  Contributors : Mathieu Brédif, Olivier Tournaire, Didier Boldo
  email : librjmcmc@ign.fr
  
  This software is a generic C++ library for stochastic optimization.
  
  This software is governed by the CeCILL license under French law and
  abiding by the rules of distribution of free software. You can use,
  modify and/or redistribute the software under the terms of the CeCILL
  license as circulated by CEA, CNRS and INRIA at the following URL
  "http://www.cecill.info".
  
  As a counterpart to the access to the source code and rights to copy,
  modify and redistribute granted by the license, users are provided only
  with a limited warranty and the software's author, the holder of the
  economic rights, and the successive licensors have only limited liability.
  
  In this respect, the user's attention is drawn to the risks associated
  with loading, using, modifying and/or developing or reproducing the
  software by the user in light of its specific status of free software,
  that may mean that it is complicated to manipulate, and that also
  therefore means that it is reserved for developers and experienced
  professionals having in-depth computer knowledge. Users are therefore
  encouraged to load and test the software's suitability as regards their
  requirements in conditions enabling the security of their systems and/or
  data to be ensured and, more generally, to use and operate it in the
  same conditions as regards security.
  
  The fact that you are presently reading this means that you have had
  knowledge of the CeCILL license and that you accept its terms.
  
  ***********************************************************************/
  
  #ifndef GEOMETRIC_SCHEDULE_HPP
  #define GEOMETRIC_SCHEDULE_HPP
  
  #include <iterator>
  
  namespace simulated_annealing {
      /**
       * \ingroup GroupSchedule
       *
       * This class is a model of the Schedule concept and implements a geometric schedule:
       * \f[T_i=T_0*\alpha^i\f]
       * This schedule does not guarantee that the simulated annealing will converge to the global optimum.
       * It is however the most commonly used schedule with a decrease coefficient close to 1 (e.g. 0.99999).
       */
      template<typename T>
      class geometric_schedule {
          
      public:
          typedef std::input_iterator_tag iterator_category;
          typedef T                       value_type;
          typedef std::ptrdiff_t          difference_type;
          typedef value_type*             pointer;
          typedef value_type&             reference;
  
          bool operator==(const geometric_schedule<T>& s) const { return (m_temp==s.m_temp) && (m_alpha==s.m_alpha); }
          bool operator!=(const geometric_schedule<T>& s) const { return !(*this==s); }
  
          /// @param temp Initial temperature
          /// @param alpha Geometric decrease coefficient
          geometric_schedule(value_type temp, value_type alpha) : m_temp(temp), m_alpha(alpha) {}
  
          inline value_type  operator*() const { return m_temp; }
          inline geometric_schedule<T>& operator++()    { m_temp *= m_alpha; return *this; }
          inline geometric_schedule<T>  operator++(int) { geometric_schedule<T> t(*this); m_temp *= m_alpha; return t; }
  
          inline value_type alpha() const { return m_alpha; }
          inline void alpha(value_type a) { m_alpha = a; }
  
      private:
          // Current temperature
          value_type m_temp;
          // Geometric decrease coefficient
          value_type m_alpha;
      };
  
  }; // namespace simulated_annealing
  
  #endif // GEOMETRIC_SCHEDULE_HPP
  