50 lines
1.7 KiB
C++
50 lines
1.7 KiB
C++
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/// @file grotto/piecewise.hpp
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/// @author Ryan Henry <ryan.henry@ucalgary.ca>
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/// @brief
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/// @details
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/// @copyright Copyright (c) 2019-2023 Ryan Henry and others
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/// @license Released under a GNU General Public v2.0 (GPLv2) license;
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/// see [LICENSE.md](@ref GPLv2) for details.
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#ifndef LIBDPF_INCLUDE_GROTTO_PIECEWISE_HPP__
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#define LIBDPF_INCLUDE_GROTTO_PIECEWISE_HPP__
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#include <array>
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#include <iterator>
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#include <algorithm>
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namespace grotto
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{
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namespace polynomials
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{
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template <typename T> using poly_constant = std::array<T, 1>;
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template <typename T> using poly_linear = std::array<T, 2>;
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template <typename T> using poly_quadratic = std::array<T, 3>;
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template <typename T> using poly_cubic = std::array<T, 4>;
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template <typename T>
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constexpr auto eval_horner(const poly_constant<T> & f, T x) { return f[0]; }
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template <typename T>
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constexpr auto eval_horner(const poly_linear<T> & f, T x) { return f[1] * x + f[0]; }
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template <typename T>
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constexpr auto eval_horner(const poly_quadratic<T> & f, T x) { return (f[2] * x + f[1]) * x + f[0]; }
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template <typename T>
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constexpr auto eval_horner(const poly_cubic<T> & f, T x) { return ((f[3] * x + f[2]) * x + f[1]) * x + f[0]; }
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template <typename T, std::size_t D, std::size_t N1, std::size_t N2>
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auto piecewise_eval(const std::array<std::array<T, D>, N1> & polys, const std::array<T, N2> & bounds, T x)
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{
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auto it = std::upper_bound(std::cbegin(bounds), std::cend(bounds), x,
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[](const T & lhs, const T & rhs){ return lhs < rhs; });
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auto i = std::distance(std::cbegin(bounds), it);
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return eval_horner(polys[i], x);
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}
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} // namespace polynomials
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} // namespace grotto
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#endif // LIBDPF_INCLUDE_GROTTO_PIECEWISE_HPP__
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