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25 //
26 // G4VGaussianQuadrature class implementation
27 //
28 // Author: V.Grichine, 18.04.1997
29 // --------------------------------------------------------------------
30
31 #include "G4VGaussianQuadrature.hh"
32 #include "G4ios.hh"
33 #include "globals.hh"
34
35 G4VGaussianQuadrature::G4VGaussianQuadrature(function pFunction)
36 : fFunction(pFunction)
37 {}
38
39 // -------------------------------------------------------------------
40 //
41 // Virtual destructor which deletes dynamically allocated memory
42 //
43
44 G4VGaussianQuadrature::~G4VGaussianQuadrature()
45 {
46 delete[] fAbscissa;
47 delete[] fWeight;
48 }
49
50 // -------------------------- Access functions
51 // ----------------------------------
52
53 G4double G4VGaussianQuadrature::GetAbscissa(G4int index) const
54 {
55 return fAbscissa[index];
56 }
57
58 G4double G4VGaussianQuadrature::GetWeight(G4int index) const
59 {
60 return fWeight[index];
61 }
62
63 G4int G4VGaussianQuadrature::GetNumber() const { return fNumber; }
64
65 // ----------------------------------------------------------------------------
66 //
67 // Auxiliary function which returns the value of std::log(gamma-function(x))
68 //
69
70 G4double G4VGaussianQuadrature::GammaLogarithm(G4double xx)
71 {
72 // Returns the value ln(Gamma(xx) for xx > 0. Full accuracy is obtained for
73 // xx > 1. For 0 < xx < 1. the reflection formula (6.1.4) can be used first.
74 // (Adapted from Numerical Recipes in C)
75
76 static const G4double cof[6] = { 76.18009172947146, -86.50532032941677,
77 24.01409824083091, -1.231739572450155,
78 0.1208650973866179e-2, -0.5395239384953e-5 };
79 G4double x = xx - 1.0;
80 G4double tmp = x + 5.5;
81 tmp -= (x + 0.5) * std::log(tmp);
82 G4double ser = 1.000000000190015;
83
84 for(size_t j = 0; j <= 5; ++j)
85 {
86 x += 1.0;
87 ser += cof[j] / x;
88 }
89 return -tmp + std::log(2.5066282746310005 * ser);
90 }
91