Histogram.h

#pragma once
 
#include <algorithm>
#include <cassert>
#include <chrono>
#include <cmath>
#include <map>
 
namespace xrpl {
namespace test {
namespace csf {
 
template <class T, class Compare = std::less<T>>
class Histogram
{
    // TODO: Consider logarithmic bins around expected median if this becomes
    // unscalable
    std::map<T, std::size_t, Compare> counts_;
    std::size_t samples = 0;
 
public:
    void
    insert(T const& s)
    {
        ++counts_[s];
        ++samples;
    }
 
    std::size_t
    size() const
    {
        return samples;
    }
 
    std::size_t
    numBins() const
    {
        return counts_.size();
    }
 
    T
    minValue() const
    {
        return counts_.empty() ? T{} : counts_.begin()->first;
    }
 
    T
    maxValue() const
    {
        return counts_.empty() ? T{} : counts_.rbegin()->first;
    }
 
    T
    avg() const
    {
        T tmp{};
        if (samples == 0)
            return tmp;
        // Since counts are sorted, shouldn't need to worry much about numerical
        // error
        for (auto const& [bin, count] : counts_)
        {
            tmp += bin * count;
        }
        return tmp / samples;
    }
 
    T
    percentile(float p) const
    {
        assert(p >= 0 && p <= 1);
        std::size_t pos = std::round(p * samples);
 
        if (counts_.empty())
            return T{};
 
        auto it = counts_.begin();
        std::size_t cumsum = it->second;
        while (it != counts_.end() && cumsum < pos)
        {
            ++it;
            cumsum += it->second;
        }
        return it->first;
    }
};
 
}  // namespace csf
}  // namespace test
}  // namespace xrpl