Geant4  v4-10.4-release
G4SmpTerrell.cc
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51 // Copyright (c) 2006 The Regents of the University of California.
53 // UCRL-CODE-224807
54 //
55 //
56 // $Id: G4SmpTerrell.cc 67966 2013-03-13 09:38:38Z gcosmo$
57 //
58
59 #include <cmath>
60 #include "G4Exp.hh"
61 #include "G4Log.hh"
62 #include "G4fissionEvent.hh"
63
64 #define TWOPI 6.283185307
65 #define SQRT2 1.414213562
66 #define BSHIFT -0.43287
67 #define WIDTH 1.079
68
70 /*
71  Description
72  Sample Fission Number from Terrell's modified Gaussian distribution
73
74  method uses Red Cullen's algoritm UCRL-TR-222526
75 */
76
77 /*
78  Input
79  nubar - average number of neutrons per fission
80  Output
81  G4SmpTerrell - sampled multiplicity
82
83 */
84
86  G4double temp1, temp2, expo, cshift;
87  G4double rw, theta, sampleg;
88
89
90  if (nubar < WIDTH) {
91  std::ostringstream o;
92  o << nubar;
93  std::string errMsg = "fission nubar out of range, nubar=" + o.str();
94  G4fissionerr(6, "SmpTerrell", errMsg);
95  }
96
97  width = SQRT2 * WIDTH;
98  temp1 = nubar + 0.5;
99  temp2 = temp1/width;
100  temp2 *= temp2;
101  expo = G4Exp(-temp2);
102  cshift = temp1 + BSHIFT * WIDTH * expo/(1. - expo);
103
104  G4int icounter = 0;
105  G4int icounter_max = 1024;
106  do {
107  rw = std::sqrt(-G4Log(fisslibrng()));
108  theta = TWOPI * fisslibrng();
109  sampleg = width * rw * std::cos(theta) + cshift;
110  icounter++;
111  if ( icounter > icounter_max ) {
112  G4cout << "Loop-counter exceeded the threshold value at " << __LINE__ << "th line of " << __FILE__ << "." << G4endl;
113  break;
114  }
115  } while (sampleg < 0.0);
116  // Loop checking, 11.03.2015, T. Koi
117
118  return std::floor(sampleg);
119 }
G4double G4Exp(G4double initial_x)
Exponential Function double precision.
Definition: G4Exp.hh:183
#define WIDTH
Definition: G4SmpTerrell.cc:67
#define G4endl
Definition: G4ios.hh:61
G4double G4Log(G4double x)
Definition: G4Log.hh:230
double G4double
Definition: G4Types.hh:76
#define width
#define BSHIFT
Definition: G4SmpTerrell.cc:66
#define TWOPI
Definition: G4SmpTerrell.cc:64
void G4fissionerr(G4int iSever, std::string chSubNam, std::string chMsg)
Definition: G4fissionerr.cc:65
int G4int
Definition: G4Types.hh:78
G4GLOB_DLL std::ostream G4cout
G4double G4SmpTerrell(G4double nubar)
Definition: G4SmpTerrell.cc:69
#define SQRT2
Definition: G4SmpTerrell.cc:65
static G4double fisslibrng(void)
Definition: G4rngc.cc:65