ChebyshevApprox.cxx

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// @(#)root/mathmore:$Id$
// Authors: L. Moneta, A. Zsenei   08/2005
 
 
 /**********************************************************************
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  * Copyright (c) 2004 ROOT Foundation,  CERN/PH-SFT                   *
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// Implementation file for class ChebyshevApprox
//
// Created by: moneta  at Thu Dec  2 14:51:15 2004
//
// Last update: Thu Dec  2 14:51:15 2004
//
 
 
#include "Math/IFunction.h"
 
#include "Math/ChebyshevApprox.h"
#include "GSLFunctionWrapper.h"
#include "GSLChebSeries.h"
 
#include "gsl/gsl_chebyshev.h"
 
#include <cassert>
 
 
namespace ROOT {
namespace Math {
 
 
ChebyshevApprox::ChebyshevApprox(const ROOT::Math::IGenFunction & f, double a, double b, size_t n) :
   fOrder(n) , fSeries(nullptr), fFunction(nullptr)
{
   // constructor from function (IGenFunction type) and interval [a,b] and series size n
   fSeries = new GSLChebSeries(n);
   GSLFunctionAdapter<ROOT::Math::IGenFunction> adapter;
   const void * p = &f;
   Initialize(  &adapter.F, const_cast<void *>(p), a, b );
}
 
// constructor with GSL function
ChebyshevApprox::ChebyshevApprox(GSLFuncPointer f, void * params, double a, double b, size_t n) :
fOrder(n) , fSeries(nullptr), fFunction(nullptr)
{
   // constructor from function (GSL type) and interval [a,b] and series size n
   fSeries = new GSLChebSeries(n);
   Initialize(  f, params, a, b );
}
 
ChebyshevApprox::~ChebyshevApprox()
{
   // destructor (clean up resources)
   if (fFunction) delete fFunction;
   if (fSeries) delete fSeries;
}
 
ChebyshevApprox::ChebyshevApprox(size_t n) :
fOrder(n) , fSeries(nullptr), fFunction(nullptr)
{
   // constructor passing only size (need to initialize setting the function afterwards)
   fSeries = new GSLChebSeries(n);
}
 
void ChebyshevApprox::Initialize( GSLFuncPointer f, void * params, double a, double b) {
   // initialize by passing a function and interval [a,b]
   // delete previous existing function pointer
   assert(fSeries != nullptr);
   if (fFunction) delete fFunction;
 
   fFunction = new GSLFunctionWrapper();
   fFunction->SetFuncPointer( f );
   fFunction->SetParams( params );
 
   // check for errors here ???
   gsl_cheb_init( fSeries->get(), fFunction->GetFunc(), a, b);
}
 
double ChebyshevApprox::operator() ( double x ) const {
   // evaluate the approximation
   return gsl_cheb_eval(fSeries->get(), x);
}
 
std::pair<double, double>  ChebyshevApprox::EvalErr( double x) const {
   // evaluate returning result and error
   double result, error;
   gsl_cheb_eval_err(fSeries->get(), x, &result, &error);
   return std::make_pair( result, error);
}
 
double ChebyshevApprox::operator() ( double x, size_t n) const {
   // evaluate at most order n ( truncate the series)
   return gsl_cheb_eval_n(fSeries->get(), n, x);
}
 
std::pair<double, double>  ChebyshevApprox::EvalErr( double x, size_t n) const {
   // evaluate at most order n ( truncate the series) returning result + error
   double result, error;
   gsl_cheb_eval_n_err(fSeries->get(), n, x, &result, &error);
   return std::make_pair( result, error);
}
 
ChebyshevApprox *ChebyshevApprox::Deriv()
{
   // calculate derivative. Returns pointer to a new series
   ChebyshevApprox *deriv = new ChebyshevApprox(fOrder);
 
   // check for errors ?
   gsl_cheb_calc_deriv((deriv->fSeries)->get(), fSeries->get());
   return deriv;
}
 
ChebyshevApprox *ChebyshevApprox::Integral()
{
   // integral (return pointer)
   ChebyshevApprox *integ = new ChebyshevApprox(fOrder);
 
   // check for errors ?
   gsl_cheb_calc_integ((integ->fSeries)->get(), fSeries->get());
   return integ;
}
 
} // namespace Math
} // namespace ROOT