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libmultiscale/src/math/spline_function.hh
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spline_function.hh
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/**
* @file spline_function.hh
*
* @author Srinivasa Babu Ramisetti <srinivasa.ramisetti@epfl.ch>
* @author Guillaume Anciaux <guillaume.anciaux@epfl.ch>
*
* @date Wed Dec 04 12:14:29 2013
*
* @brief This is a generic function using a spline interpolation
*
* @section LICENSE
*
* Copyright (©) 2010-2011 EPFL (Ecole Polytechnique Fédérale de Lausanne)
* Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
*
* LibMultiScale is free software: you can redistribute it and/or modify it
* under the
* terms of the GNU Lesser General Public License as published by the Free
* Software Foundation, either version 3 of the License, or (at your option) any
* later version.
*
* LibMultiScale is distributed in the hope that it will be useful, but
* WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
* A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
* details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with LibMultiScale. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef __LIBMULTISCALE_SPLINE_FUNCTION_HH__
#define __LIBMULTISCALE_SPLINE_FUNCTION_HH__
/* -------------------------------------------------------------------------- */
#include "cubic_spline.hh"
/* -------------------------------------------------------------------------- */
__BEGIN_LIBMULTISCALE__
/** Class SplineFunction
*
* This class permits to take an analytical function and
* generates regular points over a domain to allow spline
* interpolation
*/
template <typename Function> class SplineFunction {
/* ------------------------------------------------------------------------ */
/* Constructors/Destructors */
/* ------------------------------------------------------------------------ */
public:
SplineFunction(Function &f) : func(f){};
virtual ~SplineFunction(){};
/* ------------------------------------------------------------------------ */
/* Methods */
/* ------------------------------------------------------------------------ */
public:
template <UInt derivation_order> inline Real compute(Real x);
void init(Real min, Real max, UInt n_points, UInt max_order);
template <UInt derivation_order> void initSample(std::vector<Real> &f);
/* ------------------------------------------------------------------------ */
/* Accessors */
/* ------------------------------------------------------------------------ */
public:
/* ------------------------------------------------------------------------ */
/* Class Members */
/* ------------------------------------------------------------------------ */
private:
Function func;
//! x coordinates
std::vector<Real> x;
//! per derivation order sample of the function
std::vector<std::vector<Real>> samples;
//! per derivation order spline objects
std::vector<CubicSpline> splines;
};
/* -------------------------------------------------------------------------- */
template <typename Function>
template <UInt order>
inline Real SplineFunction<Function>::compute(Real x) {
Real res = 0.0;
splines[order].fastEvaluateSpline(x, res);
return res;
}
/* -------------------------------------------------------------------------- */
template <typename Function>
template <UInt order>
inline void SplineFunction<Function>::initSample(std::vector<Real> &f) {
// std::stringstream str;
// str << "test-function-" << order << ".gplot";
// std::ofstream file(str.str().c_str());
UInt n_points = x.size();
for (UInt i = 0; i < n_points; ++i) {
Real value = func.template compute<order>(x[i]);
f.push_back(value);
// file << x[i] << "\t" << value << std::endl;
}
// file.close();
}
/* -------------------------------------------------------------------------- */
template <typename Function>
inline void SplineFunction<Function>::init(Real min, Real max, UInt n_points,
UInt max_order) {
// make up the x coordinates
Real step = (max - min) / (n_points - 1);
x.reserve(n_points);
for (UInt i = 0; i < n_points; ++i) {
x.push_back(min + step * i);
}
samples.resize(max_order);
splines.resize(max_order);
for (UInt order = 0; order < max_order; ++order) {
std::vector<Real> &f = samples[order];
switch (order) {
case 0:
initSample<0>(f);
break;
case 1:
initSample<1>(f);
break;
case 2:
initSample<2>(f);
break;
case 3:
initSample<3>(f);
break;
default:
LM_FATAL("switch should be extended ?");
}
splines[order].buildSplineCoefficients(x, f, step);
}
}
/* -------------------------------------------------------------------------- */
__END_LIBMULTISCALE__
#endif /* __LIBMULTISCALE_SPLINE_FUNCTION_HH__ */
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