Gabriele Cosmo
104 lines
5.0 KiB
C++
104 lines
5.0 KiB
C++
//
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// ********************************************************************
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// * License and Disclaimer *
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// * *
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// * The Geant4 software is copyright of the Copyright Holders of *
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// * the Geant4 Collaboration. It is provided under the terms and *
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// * conditions of the Geant4 Software License, included in the file *
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// * LICENSE and available at http://cern.ch/geant4/license . These *
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// * include a list of copyright holders. *
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// * *
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// * Neither the authors of this software system, nor their employing *
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// * institutes,nor the agencies providing financial support for this *
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// * work make any representation or warranty, express or implied, *
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// * regarding this software system or assume any liability for its *
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// * use. Please see the license in the file LICENSE and URL above *
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// * for the full disclaimer and the limitation of liability. *
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// * *
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// * This code implementation is the result of the scientific and *
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// * technical work of the GEANT4 collaboration. *
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// * By using, copying, modifying or distributing the software (or *
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// * any work based on the software) you agree to acknowledge its *
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// * use in resulting scientific publications, and indicate your *
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// * acceptance of all terms of the Geant4 Software license. *
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// ********************************************************************
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//
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// G4ChebyshevApproximation
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//
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// Class description:
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//
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// Class creating the Chebyshev approximation for a function pointed by
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// fFunction data member. The Chebyshev polinom approximation provides an
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// efficient evaluation of minimax polynomial, which (among all polynomials of
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// the same degree) has the smallest maximum deviation from the true function.
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// The methods based mainly on recommendations given in the book : An
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// introduction to NUMERICAL METHODS IN C++, B.H. Flowers, Claredon Press,
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// Oxford, 1995
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// Author: V.Grichine, 24.04.1997
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// --------------------------------------------------------------------
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#ifndef G4CHEBYSHEVAPPROXIMATION_HH
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#define G4CHEBYSHEVAPPROXIMATION_HH 1
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#include "globals.hh"
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using function = G4double (*)(G4double);
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class G4ChebyshevApproximation
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{
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public:
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G4ChebyshevApproximation(function pFunction, G4int n, G4double a, G4double b);
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// Constructor for creation of Chebyshev coefficients for m-derivative
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// from pFunction. The value of m ! MUST BE ! < n , because the result
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// array of fChebyshevCof will be of (n-m) size.
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// It creates the array fChebyshevCof[0,...,fNumber-1], fNumber = n ;
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// which consists of Chebyshev coefficients describing the function pointed
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// by pFunction. The values a and b fixe the interval of validity of
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// Chebyshev approximation.
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G4ChebyshevApproximation(function pFunction, G4int n, G4int m, G4double a,
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G4double b);
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// Constructor for creation of Chebyshev coefficients for m-derivative
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// from pFunction. The value of m ! MUST BE ! < n , because the result
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// array of fChebyshevCof will be of (n-m) size. There is a definite
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// dependence between the proper selection of n, m, a and b values to get
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// better accuracy of the derivative value.
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G4ChebyshevApproximation(function pFunction, G4double a, G4double b, G4int n);
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// Constructor for creation of Chebyshev coefficients for integral
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// from pFunction.
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~G4ChebyshevApproximation();
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// Destructor deletes the array of Chebyshev coefficients
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G4ChebyshevApproximation(const G4ChebyshevApproximation&) = delete;
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G4ChebyshevApproximation& operator=(const G4ChebyshevApproximation&) = delete;
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// Copy constructor and assignment operator not allowed.
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G4double GetChebyshevCof(G4int number) const;
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// Access function for Chebyshev coefficients
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G4double ChebyshevEvaluation(G4double x) const;
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// Evaluate the value of fFunction at the point x via the Chebyshev
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// coefficients fChebyshevCof[0,...,fNumber-1]
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void DerivativeChebyshevCof(G4double derCof[]) const;
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// Returns the array derCof[0,...,fNumber-2], the Chebyshev coefficients
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// of the derivative of the function whose coefficients are fChebyshevCof
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void IntegralChebyshevCof(G4double integralCof[]) const;
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// This function produces the array integralCof[0,...,fNumber-1] , the
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// Chebyshev coefficients of the integral of the function whose coefficients
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// are fChebyshevCof. The constant of integration is set so that the integral
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// vanishes at the point (fMean - fDiff)
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private:
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function fFunction; // pointer to a function considered
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G4int fNumber; // number of Chebyshev coefficients
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G4double* fChebyshevCof; // array of Chebyshev coefficients
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G4double fMean; // (a+b)/2 - mean point of interval
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G4double fDiff; // (b-a)/2 - half of the interval value
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};
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#endif
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