| Geant4 Cross Reference |
1 // -*- C++ -*- 1 // -*- C++ -*-
2 // 2 //
3 // ------------------------------------------- 3 // -----------------------------------------------------------------------
4 // HEP Random 4 // HEP Random
5 // --- HepStat --- 5 // --- HepStat ---
6 // Purely static class containing use 6 // Purely static class containing useful statistics methods
7 7
8 // ------------------------------------------- 8 // -----------------------------------------------------------------------
9 9
10 // HepStat is a substitute for using a namespa 10 // HepStat is a substitute for using a namespace.
11 // One would never instantiate a HepStat objec 11 // One would never instantiate a HepStat object;
12 // usage of any of these methods looks like -- 12 // usage of any of these methods looks like --
13 // 13 //
14 // double x = HepStat::erf ( .1 ); 14 // double x = HepStat::erf ( .1 );
15 // 15 //
16 // A user may wish to improve the readability 16 // A user may wish to improve the readability of algortihm code which uses
17 // one method many times by lines like using H 17 // one method many times by lines like using HepStat::erf
18 // 18 //
19 // and later, x = erf(u); will work. 19 // and later, x = erf(u); will work.
20 // 20 //
21 21
22 // These methods are implemented in separate . 22 // These methods are implemented in separate .cc files so that
23 // user code need pull in only the code that i 23 // user code need pull in only the code that is necessary. Time
24 // (ROUGH estimates in cycles) and table footp 24 // (ROUGH estimates in cycles) and table footprint info is provided
25 // in this header. 25 // in this header.
26 26
27 27
28 // =========================================== 28 // =======================================================================
29 // M. Fischler - Created: 1/25/00 29 // M. Fischler - Created: 1/25/00
30 // 30 //
31 // M. Fischler - Inserted flatToGaussian 1/ 31 // M. Fischler - Inserted flatToGaussian 1/25/00
32 // From code of an attempt to speed u 32 // From code of an attempt to speed up RandGauss
33 // by use of tables and splines. The 33 // by use of tables and splines. The code was not
34 // significantly faster than Box- 34 // significantly faster than Box-Mueller, so that
35 // algorithm is left as the RandG 35 // algorithm is left as the RandGauss implementation.
36 // - Inserted inverseErf 36 // - Inserted inverseErf
37 // M. Fischler - Inserted gammln 2/4/00 37 // M. Fischler - Inserted gammln 2/4/00
38 // M. Fischler - Made constructor private; 38 // M. Fischler - Made constructor private; removed private destructor 4/17/00
39 // =========================================== 39 // =======================================================================
40 40
41 #ifndef HepStat_h 41 #ifndef HepStat_h
42 #define HepStat_h 1 42 #define HepStat_h 1
43 43
44 namespace CLHEP { 44 namespace CLHEP {
45 45
46 /** 46 /**
47 * @author 47 * @author
48 * @ingroup random 48 * @ingroup random
49 */ 49 */
50 class HepStat { 50 class HepStat {
51 51
52 private: 52 private:
53 HepStat(); 53 HepStat();
54 // You CANNOT instantiate a HepStat object. 54 // You CANNOT instantiate a HepStat object.
55 55
56 public: 56 public:
57 57
58 static double flatToGaussian (double r); 58 static double flatToGaussian (double r);
59 // This is defined by the satement that if 59 // This is defined by the satement that if e() provides a uniform random
60 // on (0,1) then flatToGaussian(e()) is dis 60 // on (0,1) then flatToGaussian(e()) is distributed as a unit normal
61 // Gaussian. That is, flatToGaussian is th 61 // Gaussian. That is, flatToGaussian is the inverse of the c.d.f. of
62 // a Gaussian. 62 // a Gaussian.
63 // Footprint: 30 K // Time: 150 cycl 63 // Footprint: 30 K // Time: 150 cycles
64 64
65 static double inverseErf (double t); 65 static double inverseErf (double t);
66 static double erf (double x); 66 static double erf (double x);
67 // defined in flatToGaussian.cc 67 // defined in flatToGaussian.cc
68 68
69 static double erfQ (double x); 69 static double erfQ (double x);
70 // Quicker, and with less footprint, than er 70 // Quicker, and with less footprint, than erf and gaussianCDF
71 // but only accurate to 7 digits. 71 // but only accurate to 7 digits.
72 // Footprint: 0 // Time: 72 // Footprint: 0 // Time:
73 73
74 static double gammln (double x); 74 static double gammln (double x);
75 // ln (gamma(x)) 75 // ln (gamma(x))
76 76
77 }; 77 };
78 78
79 } // namespace CLHEP 79 } // namespace CLHEP
80 80
81 #endif 81 #endif
82 82