G4VGaussianQuadrature.cc

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//
// G4VGaussianQuadrature class implementation
//
// Author: V.Grichine, 18.04.1997
// --------------------------------------------------------------------
 
#include "G4VGaussianQuadrature.hh"
#include "G4ios.hh"
#include "globals.hh"
 
G4VGaussianQuadrature::G4VGaussianQuadrature(function pFunction)
  : fFunction(pFunction)
{}
 
// -------------------------------------------------------------------
//
// Virtual destructor which deletes dynamically allocated memory
//
 
G4VGaussianQuadrature::~G4VGaussianQuadrature()
{
  delete[] fAbscissa;
  delete[] fWeight;
}
 
// -------------------------- Access functions
// ----------------------------------
 
G4double G4VGaussianQuadrature::GetAbscissa(G4int index) const
{
  return fAbscissa[index];
}
 
G4double G4VGaussianQuadrature::GetWeight(G4int index) const
{
  return fWeight[index];
}
 
G4int G4VGaussianQuadrature::GetNumber() const { return fNumber; }
 
// ----------------------------------------------------------------------------
//
// Auxiliary function which returns the value of std::log(gamma-function(x))
//
 
G4double G4VGaussianQuadrature::GammaLogarithm(G4double xx)
{
  // Returns the value ln(Gamma(xx) for xx > 0.  Full accuracy is obtained for
  // xx > 1. For 0 < xx < 1. the reflection formula (6.1.4) can be used first.
  // (Adapted from Numerical Recipes in C)
 
  static const G4double cof[6] = { 76.18009172947146,     -86.50532032941677,
                                   24.01409824083091,     -1.231739572450155,
                                   0.1208650973866179e-2, -0.5395239384953e-5 };
  G4double x                   = xx - 1.0;
  G4double tmp                 = x + 5.5;
  tmp -= (x + 0.5) * std::log(tmp);
  G4double ser = 1.000000000190015;
 
  for(size_t j = 0; j <= 5; ++j)
  {
    x += 1.0;
    ser += cof[j] / x;
  }
  return -tmp + std::log(2.5066282746310005 * ser);
}