PRNVector

prnvector.h

#ifndef _PRN_VECTOR_H__
#define _PRN_VECTOR_H__

template<typename RNG>
struct UnchangedRNGDistribution {
    auto operator()(RNG &rng) const {return rng();}
    void reset() {} // For interface compatibility with generators with internal state.
};

template<typename RNG=std::mt19937_64, typename Distribution=UnchangedRNGDistribution<RNG>>
class PRNVector {
    // Vector of random values generated
    const uint64_t seed_;
[dbaker49@jhu.edu@login-node01 gfrp]$ tail -n +156 include/gfrp/compact.h 
template<typename RNG>
struct UnchangedRNGDistribution {
    auto operator()(RNG &rng) const {return rng();}
    void reset() {} // Because RNGs such as std::normal_distribution have an internal state to reset, this is provided for interface compatibility.
};

template<typename RNG=aes::AesCtr, typename Distribution=UnchangedRNGDistribution<RNG>>
class PRNVector {
    // Vector of random values generated
    const uint64_t seed_;
    uint64_t       used_;
    uint64_t       size_;
    RNG             rng_;
    Distribution   dist_;
public:
    using ResultType = std::decay_t<decltype(dist_(rng_))>;
private:
    ResultType      val_;


public:

    class PRNIterator {

        PRNVector<RNG, Distribution> *const ref_;
    public:
        auto operator*() const {return ref_->val_;}
        auto &operator ++() {
            inc();
            return *this;
        }
        void inc() {
            ref_->gen();
            ++ref_->used_;
        }
        void gen() {ref_->gen();}
        bool operator !=(const PRNIterator &other) const {
            return ref_->used_ < ref_->size_; // Doesn't even access the other iterator. Only used for `while(it < end)`.
        }
        PRNIterator(PRNVector<RNG, Distribution> *prn_vec): ref_(prn_vec) {}
    };

    template<typename... DistArgs>
    PRNVector(uint64_t size, uint64_t seed=0, DistArgs &&... args):
        seed_{seed}, used_{0}, size_{size}, rng_(seed_), dist_(std::forward<DistArgs>(args)...), val_(gen()) {}

    auto begin() {
        reset();
        return PRNIterator(this);
    }
    ResultType gen() {return val_ = dist_(rng_);}
    void reset() {
        rng_.seed(seed_);
        dist_.reset();
        used_ = 0;
        gen();
    }
    auto end() {
        return PRNIterator(static_cast<decltype(this)>(nullptr));
    }
    auto end() const {
        return PRNIterator(static_cast<decltype(this)>(nullptr));
    }
    auto size() const {return size_;}
    void resize(size_t newsize) {size_ = newsize;}
};

#endif // #ifndef _PRN_VECTOR_H__