Gabriele Cosmo
87 lines
2.0 KiB
C++
87 lines
2.0 KiB
C++
// This code implementation is the intellectual property of
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// the GEANT4 collaboration.
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//
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// By copying, distributing or modifying the Program (or any work
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// based on the Program) you indicate your acceptance of this statement,
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// and all its terms.
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//
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// $Id: G4VGaussianQuadrature.cc,v 1.2 1999/11/16 17:31:11 gcosmo Exp $
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// GEANT4 tag $Name: geant4-03-00 $
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//
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// Implementation file for G4VGaussianQuadrature virtual base class
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//
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#include "G4ios.hh"
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#include "globals.hh"
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#include "G4VGaussianQuadrature.hh"
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G4VGaussianQuadrature::G4VGaussianQuadrature( function pFunction )
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{
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fFunction = pFunction ;
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fAbscissa = 0;
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fWeight = 0;
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}
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// -------------------------------------------------------------------
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//
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// Virtual destructor which deletes dynamically allocated memory
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//
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G4VGaussianQuadrature::~G4VGaussianQuadrature()
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{
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delete[] fAbscissa ;
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delete[] fWeight ;
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}
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// -------------------------- Access functions ----------------------------------
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G4double
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G4VGaussianQuadrature::GetAbscissa(G4int index) const
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{
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return fAbscissa[index] ;
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}
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G4double
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G4VGaussianQuadrature::GetWeight(G4int index) const
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{
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return fWeight[index] ;
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}
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// ----------------------------------------------------------------------------
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//
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// Auxiliary function which returns the value of log(gamma-function(x))
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//
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G4double
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G4VGaussianQuadrature::GammaLogarithm(G4double xx)
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{
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// Returns the value ln(Gamma(xx) for xx > 0. Full accuracy is obtained for
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// xx > 1. For 0 < xx < 1. the reflection formula (6.1.4) can be used first.
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// (Adapted from Numerical Recipes in C)
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static G4double cof[6] = { 76.18009172947146, -86.50532032941677,
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24.01409824083091, -1.231739572450155,
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0.1208650973866179e-2, -0.5395239384953e-5 } ;
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register HepInt j;
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G4double x = xx - 1.0;
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G4double tmp = x + 5.5;
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tmp -= (x + 0.5) * log(tmp);
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G4double ser = 1.000000000190015;
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for ( j = 0; j <= 5; j++ )
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{
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x += 1.0;
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ser += cof[j]/x;
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}
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return -tmp + log(2.5066282746310005*ser);
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}
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