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https://github.com/gwm17/catima.git
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94 lines
2.9 KiB
C++
94 lines
2.9 KiB
C++
/*
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*
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* This is modification of Tino Kluge tk spline
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* calculation is optimized for tridiagonal matrices
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*
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* Copyright(C) 2017
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef TK_SPLINE_H
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#define TK_SPLINE_H
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#include <cstdio>
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#include <cassert>
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#include <vector>
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#include <algorithm>
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namespace catima
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{
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// band matrix solver
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class band_matrix
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{
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private:
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std::vector<double> a;
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std::vector<double> d;
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std::vector<double> c;
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std::vector<double> save;
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public:
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band_matrix() {}; // constructor
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band_matrix(int dim); // constructor
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~band_matrix() {}; // destructor
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void resize(int dim); // init with dim,n_u,n_l
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int dim() const; // matrix dimension
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// access operator
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double & operator () (int i, int j); // write
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double operator () (int i, int j) const; // read
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// we can store an additional diogonal (in m_lower)
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std::vector<double> trig_solve(const std::vector<double>& b) const;
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};
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// spline interpolation
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class spline
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{
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public:
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enum class bd_type {
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first_deriv = 1,
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second_deriv = 2
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};
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private:
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const double *m_x, *m_y; // x,y coordinates of points
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size_t n=0;
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// interpolation parameters
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// f(x) = a*(x-x_i)^3 + b*(x-x_i)^2 + c*(x-x_i) + y_i
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std::vector<double> m_a,m_b,m_c; // spline coefficients
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double m_b0, m_c0; // for left extrapol
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bd_type m_left = bd_type::second_deriv;
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bd_type m_right = bd_type::second_deriv;
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double m_left_value = 0.0;
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double m_right_value = 0.0;
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bool m_force_linear_extrapolation = false;
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public:
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// set default boundary condition to be zero curvature at both ends
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spline(){}
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// optional, but if called it has to come be before set_points()
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void set_boundary(bd_type left, double left_value,
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bd_type right, double right_value,
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bool force_linear_extrapolation=false);
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void set_points(const double *x,
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const double *y,
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const size_t num);
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double operator() (double x) const;
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double deriv(int order, double x) const;
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};
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} // namespace tk
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#endif /* TK_SPLINE_H */
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