G4GaussChebyshevQ.cc

Go to the documentation of this file.

//
// ********************************************************************
// * License and Disclaimer                                           *
// *                                                                  *
// * The  Geant4 software  is  copyright of the Copyright Holders  of *
// * the Geant4 Collaboration.  It is provided  under  the terms  and *
// * conditions of the Geant4 Software License,  included in the file *
// * LICENSE and available at  http://cern.ch/geant4/license .  These *
// * include a list of copyright holders.                             *
// *                                                                  *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work  make  any representation or  warranty, express or implied, *
// * regarding  this  software system or assume any liability for its *
// * use.  Please see the license in the file  LICENSE  and URL above *
// * for the full disclaimer and the limitation of liability.         *
// *                                                                  *
// * This  code  implementation is the result of  the  scientific and *
// * technical work of the GEANT4 collaboration.                      *
// * By using,  copying,  modifying or  distributing the software (or *
// * any work based  on the software)  you  agree  to acknowledge its *
// * use  in  resulting  scientific  publications,  and indicate your *
// * acceptance of all terms of the Geant4 Software license.          *
// ********************************************************************
//
//
// $Id$
//
#include "G4GaussChebyshevQ.hh"
#include "G4PhysicalConstants.hh"
 
// -----------------------------------------------------
//
// Constructor for Gauss-Chebyshev quadrature method
 
G4GaussChebyshevQ::G4GaussChebyshevQ( function pFunction ,
                                      G4int nChebyshev       )
   : G4VGaussianQuadrature(pFunction)
{
   fNumber = nChebyshev  ;   // Try to reduce fNumber twice ??
   G4double cof = pi/fNumber ;
   fAbscissa = new G4double[fNumber] ;
   fWeight = new G4double[fNumber] ;
   for(G4int i=0;i<fNumber;i++)
   {
      fAbscissa[i] = std::cos(cof*(i + 0.5)) ;
      fWeight[i] = cof*std::sqrt(1 - fAbscissa[i]*fAbscissa[i]) ;
   }
}
 
// ----------------------------------------------------------------------
//
 
G4GaussChebyshevQ::~G4GaussChebyshevQ()
{
}
 
// -------------------------------------------------------------------------------
//
// Integrates function pointed by fFunction from a to b by Gauss-Chebyshev 
// quadrature method
 
G4double 
G4GaussChebyshevQ::Integral(G4double a, G4double b) const 
{
   G4double xDiff=0.5*(b - a),
            xMean=0.5*(a + b),
            dx=0.0, integral=0.0 ;
   
   for(G4int i=0;i<fNumber;i++)
   {
      dx = xDiff*fAbscissa[i] ;
      integral += fWeight[i]*fFunction(xMean + dx)  ;
   }
   return integral *= xDiff ;
}