WeightedRandomSelector.h

/*
 *   Repast for High Performance Computing (Repast HPC)
 *
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 *
 *  WeightedRandomSelector.h
 *
 *  Created on: 12 June 2015
 *      Author: murphy
 */
 
#ifndef WEIGHTEDRANDOMSELECTOR_H_
#define WEIGHTEDRANDOMSELECTOR_H_
 
#include <map>
 
#include "Random.h"
 
namespace repast {
 
template<typename T>
class WeightedRandomSelector{
 
private:
 
  static bool dblComp (double lhs, double rhs) { return lhs > rhs; } // Note: we want these sorted in reverse order
 
  std::multimap<double, T*, bool(*)(double, double)>* scoresAndObjects;
  std::set<T*>*                                       contentSet;
  double                                              total;
 
public:
  WeightedRandomSelector();
 
  virtual ~WeightedRandomSelector();
 
  void set(T* instance, double score);
 
  double remove(T* instance);
 
  bool contains(T* instance);
 
  T* getRandomInstance();
 
  void clear();
 
  size_t size();
 
  void report();
 
};
 
template<typename T>
WeightedRandomSelector<T>::WeightedRandomSelector(){
  scoresAndObjects = new std::multimap<double, T*, bool(*)(double, double)>(dblComp);
  contentSet       = new std::set<T*>();
  total            = 0;
};
 
template<typename T>
WeightedRandomSelector<T>::~WeightedRandomSelector(){
  delete scoresAndObjects;
  delete contentSet;
}
 
template<typename T>
void WeightedRandomSelector<T>::set(T* instance, double score){
  remove(instance);
  if(score <= 0) return; // Setting to zero removes from set
  scoresAndObjects->emplace(score, instance);
  contentSet->emplace(instance);
  total += score;
}
 
template<typename T>
double WeightedRandomSelector<T>::remove(T* instance){
  if(contentSet->find(instance) != contentSet->end()){
    contentSet->erase(instance);
    for(typename std::multimap<double, T*>::iterator iter = scoresAndObjects->begin(); iter != scoresAndObjects->end(); iter++){
      if(iter->second == instance){
        double score = iter->first;
        total -= score;
        scoresAndObjects->erase(iter);
        return score;
      }
    }
  }
  return 0;
}
 
template<typename T>
bool WeightedRandomSelector<T>::contains(T* instance){
  return contentSet->find() != contentSet->end();
}
 
template<typename T>
T* WeightedRandomSelector<T>::getRandomInstance(){
  if(scoresAndObjects->size() == 0) return 0;
  double val = Random::instance()->nextDouble() * total;
  double sum = 0;
  for(typename std::multimap<double, T*>::iterator iter = scoresAndObjects->begin(); iter != scoresAndObjects->end(); iter++){
    sum += iter->first;
    if(sum > val) return iter->second;
  }
  // Can't happen, but if it did, return the last entry
  typename std::multimap<double, T*>::iterator iter = scoresAndObjects->end();
  iter--;
  return iter->second;
}
 
template<typename T>
void WeightedRandomSelector<T>::clear(){
  scoresAndObjects->clear();
  contentSet->clear();
  total = 0;
}
 
template<typename T>
size_t WeightedRandomSelector<T>::size(){
  return contentSet->size();
}
 
template<typename T>
void WeightedRandomSelector<T>::report(){
  for(typename std::multimap<double, T*>::iterator iter = scoresAndObjects->begin(); iter != scoresAndObjects->end(); iter++){
    std::cout << "   " << *(iter->second) << " == " << iter->first << std::endl;
  }
}
 
 
}
 
#endif /* AGENTID_H_ */