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25 // 25 //
26 ////////////////////////////////////////////// 26 ////////////////////////////////////////////////////////////////////////////////
27 // 27 // //
28 // File: G4BetaSpectrumSampler.cc 28 // File: G4BetaSpectrumSampler.cc //
29 // Author: D.H. Wright 29 // Author: D.H. Wright //
30 // Date: 21 November 2022 30 // Date: 21 November 2022 //
31 // Description: samples a spectrum which is a 31 // Description: samples a spectrum which is a piece-wise linear function of //
32 // energy. The CDF is calculated 32 // energy. The CDF is calculated by trapezoidal integration //
33 // and within bins the line y = 33 // and within bins the line y = mx + b is sampled. //
34 // 34 // //
35 ////////////////////////////////////////////// 35 ////////////////////////////////////////////////////////////////////////////////
36 36
37 #include "G4BetaSpectrumSampler.hh" 37 #include "G4BetaSpectrumSampler.hh"
38 #include "Randomize.hh" 38 #include "Randomize.hh"
39 39
40 G4double G4BetaSpectrumSampler::shoot(const G4 40 G4double G4BetaSpectrumSampler::shoot(const G4int npoints, const G4double* aCDF,
41 const G4 41 const G4double estep)
42 { 42 {
43 G4double prob = aCDF[npoints - 1]*G4UniformR 43 G4double prob = aCDF[npoints - 1]*G4UniformRand();
44 G4int i = 0; 44 G4int i = 0;
45 for (; i<npoints; ++i) { if (prob <= aCDF[i] 45 for (; i<npoints; ++i) { if (prob <= aCDF[i]) { break; } }
46 const G4double p1 = (i > 0) ? aCDF[i - 1] : 46 const G4double p1 = (i > 0) ? aCDF[i - 1] : aCDF[0];
47 const G4double p2 = aCDF[i]; 47 const G4double p2 = aCDF[i];
48 const G4double delta = p2 - p1; 48 const G4double delta = p2 - p1;
49 const G4double x = (delta > 0.0) ? estep*i - 49 const G4double x = (delta > 0.0) ? estep*i - estep*(p2 - prob)/delta : estep*i;
50 return x; 50 return x;
51 } 51 }
52 52
53 53