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#ifndef _CCRP_H_
#define _CCRP_H_
#include <cassert>
#include <cmath>
#include <list>
#include <iostream>
#include <vector>
#include <tr1/unordered_map>
#include <boost/functional/hash.hpp>
#include "sampler.h"
// Chinese restaurant process (Pitman-Yor parameters) with explicit table
// tracking.
template <typename Dish, typename DishHash = boost::hash<Dish> >
class CCRP {
public:
CCRP(double disc, double conc) : num_tables_(), num_customers_(), discount_(disc), concentration_(conc) {}
void clear() {
num_tables_ = 0;
num_customers_ = 0;
dish_locs_.clear();
}
unsigned num_tables(const Dish& dish) const {
const typename std::tr1::unordered_map<Dish, DishLocations, DishHash>::const_iterator it = dish_locs_.find(dish);
if (it == dish_locs_.end()) return 0;
return it->second.table_counts_.size();
}
// returns +1 or 0 indicating whether a new table was opened
int increment(const Dish& dish, const double& p0, MT19937* rng) {
DishLocations& loc = dish_locs_[dish];
bool share_table = false;
if (loc.total_dish_count_) {
const double p_empty = (concentration_ + num_tables_ * discount_) * p0;
const double p_share = (loc.total_dish_count_ - loc.table_counts_.size() * discount_);
share_table = rng->SelectSample(p_empty, p_share);
}
if (share_table) {
double r = rng->next() * (loc.total_dish_count_ - loc.table_counts_.size() * discount_);
for (typename std::list<unsigned>::iterator ti = loc.table_counts_.begin();
ti != loc.table_counts_.end(); ++ti) {
r -= (*ti - discount_);
if (r <= 0.0) {
++(*ti);
break;
}
}
if (r > 0.0) {
std::cerr << "Serious error: r=" << r << std::endl;
Print(&std::cerr);
assert(r <= 0.0);
}
} else {
loc.table_counts_.push_back(1u);
++num_tables_;
}
++loc.total_dish_count_;
++num_customers_;
return (share_table ? 0 : 1);
}
// returns -1 or 0, indicating whether a table was closed
int decrement(const Dish& dish, MT19937* rng) {
DishLocations& loc = dish_locs_[dish];
assert(loc.total_dish_count_);
if (loc.total_dish_count_ == 1) {
dish_locs_.erase(dish);
--num_tables_;
--num_customers_;
return -1;
} else {
int delta = 0;
// sample customer to remove UNIFORMLY. that is, do NOT use the discount
// here. if you do, it will introduce (unwanted) bias!
double r = rng->next() * loc.total_dish_count_;
--loc.total_dish_count_;
for (typename std::list<unsigned>::iterator ti = loc.table_counts_.begin();
ti != loc.table_counts_.end(); ++ti) {
r -= *ti;
if (r <= 0.0) {
if ((--(*ti)) == 0) {
--num_tables_;
delta = -1;
loc.table_counts_.erase(ti);
}
break;
}
}
if (r > 0.0) {
std::cerr << "Serious error: r=" << r << std::endl;
Print(&std::cerr);
assert(r <= 0.0);
}
--num_customers_;
return delta;
}
}
double prob(const Dish& dish, const double& p0) const {
const typename std::tr1::unordered_map<Dish, DishLocations, DishHash>::const_iterator it = dish_locs_.find(dish);
const double r = num_tables_ * discount_ + concentration_;
if (it == dish_locs_.end()) {
return r * p0 / (num_customers_ + concentration_);
} else {
return (it->second.total_dish_count_ - discount_ * it->second.table_counts_.size() + r * p0) /
(num_customers_ + concentration_);
}
}
// taken from http://en.wikipedia.org/wiki/Chinese_restaurant_process
// does not include P_0's
double log_crp_prob() const {
double lp = 0.0;
if (num_customers_) {
const double r = lgamma(1.0 - discount_);
lp = lgamma(concentration_) - lgamma(concentration_ + num_customers_)
+ num_tables_ * discount_ + lgamma(concentration_ / discount_ + num_tables_)
- lgamma(concentration_ / discount_);
for (typename std::tr1::unordered_map<Dish, DishLocations, DishHash>::const_iterator it = dish_locs_.begin();
it != dish_locs_.end(); ++it) {
const DishLocations& cur = it->second;
lp += lgamma(cur.total_dish_count_ - discount_) - r;
}
}
return lp;
}
struct DishLocations {
DishLocations() : total_dish_count_() {}
unsigned total_dish_count_; // customers at all tables with this dish
std::list<unsigned> table_counts_; // list<> gives O(1) deletion and insertion, which we want
// .size() is the number of tables for this dish
};
void Print(std::ostream* out) const {
for (typename std::tr1::unordered_map<Dish, DishLocations, DishHash>::const_iterator it = dish_locs_.begin();
it != dish_locs_.end(); ++it) {
(*out) << it->first << " (" << it->second.total_dish_count_ << " on " << it->second.table_counts_.size() << " tables): ";
for (typename std::list<unsigned>::const_iterator i = it->second.table_counts_.begin();
i != it->second.table_counts_.end(); ++i) {
(*out) << " " << *i;
}
(*out) << std::endl;
}
}
typedef typename std::tr1::unordered_map<Dish, DishLocations, DishHash>::const_iterator const_iterator;
const_iterator begin() const {
return dish_locs_.begin();
}
const_iterator end() const {
return dish_locs_.end();
}
unsigned num_tables_;
unsigned num_customers_;
std::tr1::unordered_map<Dish, DishLocations, DishHash> dish_locs_;
double discount_;
double concentration_;
};
template <typename T,typename H>
std::ostream& operator<<(std::ostream& o, const CCRP<T,H>& c) {
c.Print(&o);
return o;
}
#endif
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