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#ifndef _CRP_H_
#define _CRP_H_
// shamelessly adapted from code by Phil Blunsom and Trevor Cohn
#include <boost/functional/hash.hpp>
#include <tr1/unordered_map>
#include "prob.h"
template <typename DishType, typename Hash = boost::hash<DishType> >
class CRP {
public:
CRP(double alpha) : alpha_(alpha), palpha_(alpha), total_customers_() {}
void increment(const DishType& dish);
void decrement(const DishType& dish);
void erase(const DishType& dish) {
counts_.erase(dish);
}
inline int count(const DishType& dish) const {
const typename MapType::const_iterator i = counts_.find(dish);
if (i == counts_.end()) return 0; else return i->second;
}
inline prob_t prob(const DishType& dish, const prob_t& p0) const {
return (prob_t(count(dish)) + palpha_ * p0) / prob_t(total_customers_ + alpha_);
}
private:
typedef std::tr1::unordered_map<DishType, int, Hash> MapType;
MapType counts_;
const double alpha_;
const prob_t palpha_;
int total_customers_;
};
template <typename Dish, typename Hash>
void CRP<Dish,Hash>::increment(const Dish& dish) {
++counts_[dish];
++total_customers_;
}
template <typename Dish, typename Hash>
void CRP<Dish,Hash>::decrement(const Dish& dish) {
typename MapType::iterator i = counts_.find(dish);
assert(i != counts_.end());
if (--i->second == 0)
counts_.erase(i);
--total_customers_;
}
#endif
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