| Geant4 Cross Reference |
>> 1 // $Id:$
1 // -*- C++ -*- 2 // -*- C++ -*-
2 // 3 //
3 // ------------------------------------------- 4 // -----------------------------------------------------------------------
4 // HEP Random 5 // HEP Random
5 // --- HepStat --- 6 // --- HepStat ---
6 // Purely static class containing use 7 // Purely static class containing useful statistics methods
7 8
8 // ------------------------------------------- 9 // -----------------------------------------------------------------------
9 10
10 // HepStat is a substitute for using a namespa 11 // HepStat is a substitute for using a namespace.
11 // One would never instantiate a HepStat objec 12 // One would never instantiate a HepStat object;
12 // usage of any of these methods looks like -- 13 // usage of any of these methods looks like --
13 // 14 //
14 // double x = HepStat::erf ( .1 ); 15 // double x = HepStat::erf ( .1 );
15 // 16 //
16 // A user may wish to improve the readability 17 // A user may wish to improve the readability of algortihm code which uses
17 // one method many times by lines like using H 18 // one method many times by lines like using HepStat::erf
18 // 19 //
19 // and later, x = erf(u); will work. 20 // and later, x = erf(u); will work.
20 // 21 //
21 22
22 // These methods are implemented in separate . 23 // These methods are implemented in separate .cc files so that
23 // user code need pull in only the code that i 24 // user code need pull in only the code that is necessary. Time
24 // (ROUGH estimates in cycles) and table footp 25 // (ROUGH estimates in cycles) and table footprint info is provided
25 // in this header. 26 // in this header.
26 27
27 28
28 // =========================================== 29 // =======================================================================
29 // M. Fischler - Created: 1/25/00 30 // M. Fischler - Created: 1/25/00
30 // 31 //
31 // M. Fischler - Inserted flatToGaussian 1/ 32 // M. Fischler - Inserted flatToGaussian 1/25/00
32 // From code of an attempt to speed u 33 // From code of an attempt to speed up RandGauss
33 // by use of tables and splines. The 34 // by use of tables and splines. The code was not
34 // significantly faster than Box- 35 // significantly faster than Box-Mueller, so that
35 // algorithm is left as the RandG 36 // algorithm is left as the RandGauss implementation.
36 // - Inserted inverseErf 37 // - Inserted inverseErf
37 // M. Fischler - Inserted gammln 2/4/00 38 // M. Fischler - Inserted gammln 2/4/00
38 // M. Fischler - Made constructor private; 39 // M. Fischler - Made constructor private; removed private destructor 4/17/00
39 // =========================================== 40 // =======================================================================
40 41
41 #ifndef HepStat_h 42 #ifndef HepStat_h
42 #define HepStat_h 1 43 #define HepStat_h 1
43 44
44 namespace CLHEP { 45 namespace CLHEP {
45 46
46 /** 47 /**
47 * @author 48 * @author
48 * @ingroup random 49 * @ingroup random
49 */ 50 */
50 class HepStat { 51 class HepStat {
51 52
52 private: 53 private:
53 HepStat(); 54 HepStat();
54 // You CANNOT instantiate a HepStat object. 55 // You CANNOT instantiate a HepStat object.
55 56
56 public: 57 public:
57 58
58 static double flatToGaussian (double r); 59 static double flatToGaussian (double r);
59 // This is defined by the satement that if 60 // This is defined by the satement that if e() provides a uniform random
60 // on (0,1) then flatToGaussian(e()) is dis 61 // on (0,1) then flatToGaussian(e()) is distributed as a unit normal
61 // Gaussian. That is, flatToGaussian is th 62 // Gaussian. That is, flatToGaussian is the inverse of the c.d.f. of
62 // a Gaussian. 63 // a Gaussian.
63 // Footprint: 30 K // Time: 150 cycl 64 // Footprint: 30 K // Time: 150 cycles
64 65
65 static double inverseErf (double t); 66 static double inverseErf (double t);
66 static double erf (double x); 67 static double erf (double x);
67 // defined in flatToGaussian.cc 68 // defined in flatToGaussian.cc
68 69
69 static double erfQ (double x); 70 static double erfQ (double x);
70 // Quicker, and with less footprint, than er 71 // Quicker, and with less footprint, than erf and gaussianCDF
71 // but only accurate to 7 digits. 72 // but only accurate to 7 digits.
72 // Footprint: 0 // Time: 73 // Footprint: 0 // Time:
73 74
74 static double gammln (double x); 75 static double gammln (double x);
75 // ln (gamma(x)) 76 // ln (gamma(x))
76 77
77 }; 78 };
78 79
79 } // namespace CLHEP 80 } // namespace CLHEP
80 81
81 #endif 82 #endif
82 83