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#ifndef _CRP_H_
#define _CRP_H_
// shamelessly adapted from code by Phil Blunsom and Trevor Cohn
// There are TWO CRP classes here: CRPWithTableTracking tracks the
// (expected) number of customers per table, and CRP just tracks
// the number of customers / dish.
// If you are implementing a HDP model, you should use CRP for the
// base distribution and CRPWithTableTracking for the dependent
// distribution.
#include <iostream>
#include <map>
#include <boost/functional/hash.hpp>
#include <tr1/unordered_map>
#include "prob.h"
#include "sampler.h" // RNG
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 {
return (prob_t(count(dish) + alpha_)) / prob_t(total_customers_ + alpha_);
}
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_;
}
template <typename DishType, typename Hash = boost::hash<DishType>, typename RNG = MT19937>
class CRPWithTableTracking {
public:
CRPWithTableTracking(double alpha, RNG* rng) :
alpha_(alpha), palpha_(alpha), total_customers_(),
total_tables_(), rng_(rng) {}
// seat a customer for dish d, returns the delta in tables
// with customers
int increment(const DishType& d, const prob_t& p0 = prob_t::One());
int decrement(const DishType& d);
void erase(const DishType& 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.count_;
}
inline prob_t prob(const DishType& dish) const {
return (prob_t(count(dish) + alpha_)) / prob_t(total_customers_ + alpha_);
}
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:
struct TableInfo {
TableInfo() : count_(), tables_() {}
int count_; // total customers eating dish
int tables_; // total tables labeled with dish
std::map<int, int> table_histogram_; // num customers at table -> number tables
};
typedef std::tr1::unordered_map<DishType, TableInfo, Hash> MapType;
inline prob_t prob_share_table(const double& customer_count) const {
if (customer_count)
return prob_t(customer_count) / prob_t(customer_count + alpha_);
else
return prob_t::Zero();
}
inline prob_t prob_new_table(const double& customer_count, const prob_t& p0) const {
if (customer_count)
return palpha_ * p0 / prob_t(customer_count + alpha_);
else
return p0;
}
MapType counts_;
const double alpha_;
const prob_t palpha_;
int total_customers_;
int total_tables_;
RNG* rng_;
};
template <typename Dish, typename Hash, typename RNG>
int CRPWithTableTracking<Dish,Hash,RNG>::increment(const Dish& dish, const prob_t& p0) {
TableInfo& tc = counts_[dish];
//std::cerr << "\nincrement for " << dish << " with p0 " << p0 << "\n";
//std::cerr << "\tBEFORE histogram: " << tc.table_histogram_ << " ";
//std::cerr << "count: " << tc.count_ << " ";
//std::cerr << "tables: " << tc.tables_ << "\n";
// seated at a new or existing table?
prob_t pshare = prob_share_table(tc.count_);
prob_t pnew = prob_new_table(tc.count_, p0);
//std::cerr << "\t\tP0 " << p0 << " count(dish) " << count(dish)
// << " tables " << tc
// << " p(share) " << pshare << " p(new) " << pnew << "\n";
int delta = 0;
if (tc.count_ == 0 || rng_->SelectSample(pshare, pnew) == 1) {
// assign to a new table
++tc.tables_;
++tc.table_histogram_[1];
++total_tables_;
delta = 1;
} else {
// can't share a table if there are no other customers
assert(tc.count_ > 0);
// randomly assign to an existing table
// remove constant denominator from inner loop
int r = static_cast<int>(rng_->next() * tc.count_);
for (std::map<int,int>::iterator hit = tc.table_histogram_.begin();
hit != tc.table_histogram_.end(); ++hit) {
r -= hit->first * hit->second;
if (r <= 0) {
++tc.table_histogram_[hit->first+1];
--hit->second;
if (hit->second == 0)
tc.table_histogram_.erase(hit);
break;
}
}
if (r > 0) {
std::cerr << "CONSISTENCY ERROR: " << tc.count_ << std::endl;
std::cerr << pshare << std::endl;
std::cerr << pnew << std::endl;
std::cerr << r << std::endl;
abort();
}
}
++tc.count_;
++total_customers_;
return delta;
}
template <typename Dish, typename Hash, typename RNG>
int CRPWithTableTracking<Dish,Hash,RNG>::decrement(const Dish& dish) {
typename MapType::iterator i = counts_.find(dish);
if(i == counts_.end()) {
std::cerr << "MISSING DISH: " << dish << std::endl;
abort();
}
int delta = 0;
TableInfo &tc = i->second;
//std::cout << "\ndecrement for " << dish << " with p0 " << p0 << "\n";
//std::cout << "\tBEFORE histogram: " << tc.table_histogram << " ";
//std::cout << "count: " << count(dish) << " ";
//std::cout << "tables: " << tc.tables << "\n";
int r = static_cast<int>(rng_->next() * tc.count_);
//std::cerr << "FOO: " << r << std::endl;
for (std::map<int,int>::iterator hit = tc.table_histogram_.begin();
hit != tc.table_histogram_.end(); ++hit) {
r -= (hit->first * hit->second);
if (r <= 0) {
if (hit->first > 1)
tc.table_histogram_[hit->first-1] += 1;
else {
--delta;
--tc.tables_;
--total_tables_;
}
--hit->second;
if (hit->second == 0) tc.table_histogram_.erase(hit);
break;
}
}
assert(r <= 0);
// remove the customer
--tc.count_;
--total_customers_;
assert(tc.count_ >= 0);
if (tc.count_ == 0) counts_.erase(i);
return delta;
}
#endif
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