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// (C) Copyright Matt Borland 2022
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0. (See accompanying file
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
#ifndef BOOST_MATH_STATISTICS_DETAIL_RANK_HPP
#define BOOST_MATH_STATISTICS_DETAIL_RANK_HPP
#include <cstdint>
#include <vector>
#include <numeric>
#include <utility>
#include <iterator>
#include <algorithm>
#include <boost/math/tools/config.hpp>
#ifdef BOOST_MATH_EXEC_COMPATIBLE
#include <execution>
#endif
namespace boost { namespace math { namespace statistics { namespace detail {
struct pair_equal
{
template <typename T1, typename T2>
bool operator()(const std::pair<T1, T2>& a, const std::pair<T1, T2>& b) const
{
return a.first == b.first;
}
};
}}}} // Namespaces
#ifndef BOOST_MATH_EXEC_COMPATIBLE
namespace boost { namespace math { namespace statistics { namespace detail {
template <typename ForwardIterator, typename T = typename std::iterator_traits<ForwardIterator>::value_type>
auto rank(ForwardIterator first, ForwardIterator last) -> std::vector<std::size_t>
{
std::size_t elements = std::distance(first, last);
std::vector<std::pair<T, std::size_t>> rank_vector(elements);
std::size_t i = 0;
while (first != last)
{
rank_vector[i] = std::make_pair(*first, i);
++i;
++first;
}
std::sort(rank_vector.begin(), rank_vector.end());
// Remove duplicates
rank_vector.erase(std::unique(rank_vector.begin(), rank_vector.end(), pair_equal()), rank_vector.end());
elements = rank_vector.size();
std::pair<T, std::size_t> rank;
std::vector<std::size_t> result(elements);
for (i = 0; i < elements; ++i)
{
if (rank_vector[i].first != rank.first)
{
rank = std::make_pair(rank_vector[i].first, i);
}
result[rank_vector[i].second] = rank.second;
}
return result;
}
template <typename Container>
inline auto rank(const Container& c) -> std::vector<std::size_t>
{
return rank(std::begin(c), std::end(c));
}
}}}} // Namespaces
#else
namespace boost::math::statistics::detail {
template <typename ExecutionPolicy, typename ForwardIterator, typename T = typename std::iterator_traits<ForwardIterator>::value_type>
auto rank(ExecutionPolicy&& exec, ForwardIterator first, ForwardIterator last)
{
std::size_t elements = std::distance(first, last);
std::vector<std::pair<T, std::size_t>> rank_vector(elements);
std::size_t i = 0;
while (first != last)
{
rank_vector[i] = std::make_pair(*first, i);
++i;
++first;
}
std::sort(exec, rank_vector.begin(), rank_vector.end());
// Remove duplicates
rank_vector.erase(std::unique(exec, rank_vector.begin(), rank_vector.end(), pair_equal()), rank_vector.end());
elements = rank_vector.size();
std::pair<T, std::size_t> rank;
std::vector<std::size_t> result(elements);
for (i = 0; i < elements; ++i)
{
if (rank_vector[i].first != rank.first)
{
rank = std::make_pair(rank_vector[i].first, i);
}
result[rank_vector[i].second] = rank.second;
}
return result;
}
template <typename ExecutionPolicy, typename Container>
inline auto rank(ExecutionPolicy&& exec, const Container& c)
{
return rank(exec, std::cbegin(c), std::cend(c));
}
template <typename ForwardIterator, typename T = typename std::iterator_traits<ForwardIterator>::value_type>
inline auto rank(ForwardIterator first, ForwardIterator last)
{
return rank(std::execution::seq, first, last);
}
template <typename Container>
inline auto rank(const Container& c)
{
return rank(std::execution::seq, std::cbegin(c), std::cend(c));
}
} // Namespaces
#endif // BOOST_MATH_EXEC_COMPATIBLE
#endif // BOOST_MATH_STATISTICS_DETAIL_RANK_HPP
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