source: lemon-0.x/src/work/akos/simann.h @ 959:c80ef5912903

#ifndef LEMON_SIMANN_H
#define LEMON_SIMANN_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() {
      while (controller->next()) {
        mutate();
        if (controller->accept()) {
          controller->acceptEvent();
          if (curr_cost < best_cost) {
            saveAsBest();
            controller->improveEvent();
          }
        }
        else {
          revert();
          controller->rejectEvent();
        }
      }
    }

    class Controller {
    public:
      SimAnnBase *base;
      virtual void acceptEvent() {}
      virtual void improveEvent() {}
      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:
    // returns the new cost
    double mutate() { return 0.0; }
    // restores the entity to its previous state i.e. reverts the effects of
    // the last mutate()
    void revert() {}
  };

  class SimpleController : public SimAnnBase::Controller {
  public:
    long iter, last_impr, max_iter, max_no_impr;
    double temp, annealing_factor;
    SimpleController() {
      iter = last_impr = 0;
      max_iter = 500000;
      max_no_impr = 20000;
      annealing_factor = 0.9999;
      temp = 1000;
    }
    void acceptEvent() {
      iter++;
    }
    void improveEvent() {
      last_impr = iter;
    }
    void rejectEvent() {
      iter++;
    }
    bool next() {
      temp *= annealing_factor;
      bool quit = (iter > max_iter) || (iter - last_impr > max_no_impr);
      return !quit;
    }
    bool accept() {
      return (drand48() <= exp(base->getPrevCost() - base->getCurrCost() / temp));
    }
  };

}

#endif