TruncatedZipfian.h

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#ifndef UTILS_TRUNCATED_ZIPFIAN_H
#define UTILS_TRUNCATED_ZIPFIAN_H
 
#include "tdb.h"
 
#include <random>
 
#include "Walker.h"
 
namespace taco {
 
class TruncatedZipfian {
public:
    using result_type = uint32_t;
    //
    // using param_type = /* something */;
 
    TruncatedZipfian():
        m_N(0) {}
 
    TruncatedZipfian(uint32_t N, double s, double prob_to_truncate);
 
    template<typename RNG>
    inline uint32_t
    operator()(RNG &rng) {
        uint32_t x = m_walker(rng);
        if (x >= m_min_in_unif) {
            x = m_unif_rem(rng);
        }
        return x;
    }
 
    constexpr uint32_t
    GetMinTruncatedItem() const {
        return m_min_in_unif;
    }
 
    double GetProbability(uint32_t x) const;
 
    constexpr double
    GetTotalTruncatedProbability() const {
        return m_total_prob_trunc;
    }
 
private:
    uint32_t    m_N;
    uint32_t    m_min_in_unif;
    double      m_s;
    double      m_H;
    double      m_total_prob_trunc;
 
    Walker      m_walker;
    std::uniform_int_distribution<uint32_t> m_unif_rem;
};
 
}   // namespace taco
 
#endif      // UTILS_TRUNCATED_ZIPFIAN_H