kopia lustrzana https://github.com/vsamy/DiFipp
32 wiersze
820 B
C++
32 wiersze
820 B
C++
#pragma once
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#include "type_checks.h"
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#include "typedefs.h"
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#include <complex>
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namespace fratio {
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template <typename T>
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struct VietaAlgo {
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static_assert(std::is_arithmetic<internal::complex_sub_type_t<T>>::value, "This struct can only accept arithmetic types or complex.");
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// Vieta's computation: https://en.wikipedia.org/wiki/Vieta%27s_formulas
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static vectX_t<T> polyCoeffFromRoot(const vectX_t<T>& poles);
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};
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template <typename T>
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vectX_t<T> VietaAlgo<T>::polyCoeffFromRoot(const vectX_t<T>& poles)
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{
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vectX_t<T> coeffs = vectX_t<T>::Zero(poles.size() + 1);
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coeffs(0) = T(1);
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for (Eigen::Index i = 0; i < poles.size(); ++i) {
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for (Eigen::Index k = i + 1; k > 0; --k) {
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coeffs(k) -= poles(i) * coeffs(k - 1);
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}
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}
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return coeffs;
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}
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} // namespace fratio
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