#ifndef LEMON_SIMANN_H

 #define LEMON_SIMANN_H

 #include <cstdlib>

 #include <cmath>

 #include <sys/time.h>

 namespace lemon {

   const double INFTY = 1e24;

   class SimAnnBase {

   public:

     class Controller;

   private:

     Controller *controller;

   protected:

     double curr_cost;

     double prev_cost;

     double best_cost;

     virtual void mutate() = 0;

     virtual void revert() = 0;

     virtual void saveAsBest() = 0;

   public:

     SimAnnBase() {

       curr_cost = prev_cost = best_cost = INFTY;

     }

     void setController(Controller &_controller) {

       controller = &_controller;

       controller->setBase(this);

     }

     double getCurrCost() { return curr_cost; }

     double getPrevCost() { return prev_cost; }

     double getBestCost() { return best_cost; }

     void run() {

       controller->init();

       while (controller->next()) {

         mutate();

         if (controller->accept()) {

           controller->acceptEvent();

           if (curr_cost < best_cost) {

             saveAsBest();

             controller->improveEvent();

           }

         }

         else {

           revert();

           controller->rejectEvent();

         }

       }

     }

     /*! \brief A base class for controllers. */

     class Controller {

     public:

       SimAnnBase *base;

       virtual void init() {}

       /*! \brief This is called when a neighbouring state gets accepted. */

       virtual void acceptEvent() {}

       /*! \brief This is called when the accepted neighbouring state's cost is

        *  less than the best found one's.

        */

       virtual void improveEvent() {}

       /*! \brief This is called when a neighbouring state gets rejected. */

       virtual void rejectEvent() {}

       virtual void setBase(SimAnnBase *_base) { base = _base; }

       /*! */

       virtual bool next() = 0;

       /*! */

       virtual bool accept() = 0;

     };

   };

   template <typename E>

   class SimAnn : public SimAnnBase {

   private:

     E *curr_ent;

     E *best_ent;

   public:

     SimAnn() : SimAnnBase() {}

     void setEntity(E &ent) {

       curr_ent = new E(ent);

       best_ent = new E(ent);

     }

     E getBestEntity() { return *best_ent; }

     void mutate() {

       curr_ent->mutate();

     }

     void revert() {

       curr_ent->revert();

     }

     void saveAsBest() {

       *best_ent = *curr_ent;

       best_cost = curr_cost;

     }

   };

   class EntitySkeleton {

   public:

     /*! \brief Makes a minor change to the entity.

      *  \return the new cost

      */

     double mutate() { return 0.0; }

     /*! \brief Restores the entity to its previous state i.e. reverts the

      *  effects of the last mutate.

      */

     void revert() {}

   };

   /*! \brief A simple controller for the simulated annealing class.

    *  \todo Find a way to set the various parameters.

    */

   class SimpleController : public SimAnnBase::Controller {

   public:

     long iter, last_impr, max_iter, max_no_impr;

     double temp, ann_fact;

     /*! \param _max_iter maximum number of iterations

      *  \param _max_no_impr maximum number of consecutive iterations which do

      *         not yield a better solution

      *  \param _temp initial temperature

      *  \param _ann_fact annealing factor

      */

     SimpleController(long _max_iter = 500000, long _max_no_impr = 20000,

     double _temp = 1000, double _ann_fact = 0.9999) : iter(0), last_impr(0),

     max_iter(_max_iter), max_no_impr(_max_no_impr), temp(_temp),

     ann_fact(_ann_fact) {}

     void acceptEvent() {

       iter++;

     }

     void improveEvent() {

       last_impr = iter;

     }

     void rejectEvent() {

       iter++;

     }

     bool next() {

       temp *= ann_fact;

       bool quit = (iter > max_iter) || (iter - last_impr > max_no_impr);

       return !quit;

     }

     bool accept() {

       return (drand48() <= exp(base->getPrevCost() - base->getCurrCost() /

         temp));

     }

   };

   /*! \brief A controller with preset running time for the simulated annealing

    *  class.

    *  \todo Find a better name.

    */

   class AdvancedController : public SimAnnBase::Controller {

   private:

     /*! \param time the elapsed time in seconds */

     double threshold(double time) { return 0.0; }

   public:

     double alpha, beta, gamma;

     double end_time, start_time;

     double avg_cost;

     double temp, ann_fact;

     /*! \param _end_time running_time

      *  \param _alpha parameter used to calculate the running average

      *  \param _beta parameter used to decrease the annealing factor

      *  \param _gamma parameter used to increase the temperature

      */

     AdvancedController(double _end_time, double _alpha = 0.2,

     double _beta = 0.9, double _gamma = 1.2) : alpha(_alpha), beta(_beta),

     gamma(_gamma), end_time(_end_time) {}

     void init() {

       timeval tv;

       gettimeofday(&tv, 0);

       start_time = tv.tv_sec + double(tv.tv_usec) / 1e6;

     }

     void acceptEvent() {

       avg_cost = alpha * base->getCurrCost() + (1.0 - alpha) * avg_cost;

     }

     void improveEvent() {

     }

     void rejectEvent() {

     }

     bool next() {

       timeval tv;

       gettimeofday(&tv, 0);

       double elapsed_time = tv.tv_sec + double(tv.tv_usec) / 1e6 - start_time;

       if (fabs(avg_cost - base->getBestCost()) > threshold(elapsed_time)) {

 	// decrease the annealing factor

         ann_fact *= beta;

       }

       else {

         // increase the temperature

         temp *= gamma;

       }

       temp *= ann_fact;

       return elapsed_time < end_time;

     }

     bool accept() {

       return (drand48() <= exp(base->getPrevCost() - base->getCurrCost() /

         temp));

     }

   };

 }

 #endif