| Geant4 Cross Reference |
1 // -*- C++ -*- 1
2 //
3 // -------------------------------------------
4 // HEP Random
5 // --- RandPoissonQ --
6 // class header file
7 // -------------------------------------------
8
9 // Class defining RandPoissonQ, which is deriv
10 // The user interface is identical; but RandGa
11 // and a bit less accurate when mu > 100.
12
13 // ===========================================
14 // M. Fischler - Created: 4th Feb 2000
15 // M Fischler - put and get to/from strea
16 //
17 // ===========================================
18
19 #ifndef RandPoissonQ_h
20 #define RandPoissonQ_h 1
21
22 #include "CLHEP/Random/Random.h"
23 #include "CLHEP/Random/RandPoisson.h"
24
25 namespace CLHEP {
26
27 /**
28 * @author
29 * @ingroup random
30 */
31 class RandPoissonQ : public RandPoisson {
32
33 public:
34
35 inline RandPoissonQ ( HepRandomEngine& anEng
36 inline RandPoissonQ ( HepRandomEngine* anEng
37 // These constructors should be used to inst
38 // distribution object defining a local engi
39 // The static generator will be skipped usin
40 // defined below.
41 // If the engine is passed by pointer the co
42 // will be deleted by the RandPoissonQ destr
43 // If the engine is passed by reference the
44 // will not be deleted by the RandPoissonQ d
45
46 virtual ~RandPoissonQ();
47 // Destructor
48
49 // Save and restore to/from streams
50
51 std::ostream & put ( std::ostream & os ) con
52 std::istream & get ( std::istream & is );
53
54 // Methods to generate Poisson-distributed r
55
56 // The method used for mu <= 100 is exact,
57 // that used by RandPoisson.
58 // For mu > 100 then we use a corrected ve
59 // (quick) Gaussian approximation. Naivel
60 //
61 // Poisson(mu) ~ floor( mu + .5 + Gaussian(
62 //
63 // but actually, that would give a slightl
64 // very different skew than a true Poisson
65 //
66 // Poisson(mu) ~ floor( a0*mu + a1*g + a2*g
67 // (with g a gaussian normal)
68 //
69 // where a0, a1, a2 are chosen to give the
70 // and skew for the Poisson distribution.
71
72 // Static methods to shoot random values usi
73
74 static long shoot( double mean=1.0 );
75
76 static void shootArray ( const int size, lo
77
78 // Static methods to shoot random values us
79 // by-passing the static generator.
80
81 static long shoot( HepRandomEngine* anEngin
82
83 static void shootArray ( HepRandomEngine* a
84 const int size, lo
85
86 // Methods using the localEngine to shoot r
87 // the static generator.
88
89 long fire();
90 long fire( double mean );
91
92 void fireArray ( const int size, long* vect
93 void fireArray ( const int size, long* vect,
94
95 double operator()();
96 double operator()( double mean );
97
98 std::string name() const;
99 HepRandomEngine & engine();
100
101 static std::string distributionName() {retur
102 // Provides the name of this distribution cl
103
104
105 // static constants of possible interest to
106
107 // RandPoisson will never return a deviate g
108 static const double MAXIMUM_POISSON_DEVIATE;
109
110 static inline int tableBoundary();
111
112 private:
113
114 // constructor helper
115 void setupForDefaultMu();
116
117 // algorithm helper methods - all static sin
118 static long poissonDeviateSmall ( HepRandomE
119 static long poissonDeviateQuick ( HepRandomE
120 static long poissonDeviateQuick ( HepRandomE
121 double A0, double A1, double A2, double si
122
123 // All the engine info, and the default mean
124 // RandPoisson base class.
125
126 // quantities for approximate Poisson by cor
127 double a0;
128 double a1;
129 double a2;
130 double sigma;
131
132 // static data - constants only, so that sav
133
134 // The following MUST MATCH the correspondin
135 // poissonTables.cc) when poissonTables.cdat
136 // poissonTables.cc gets these values by inc
137 // but we must be careful not to change thes
138 // and rebuild RandPoissonQ before re-genera
139
140 // (These statics are given values near the
141
142 static const double FIRST_MU; // lowest mu
143 static const double LAST_MU; // highest mu
144 static const double S; // Spacing be
145 static const int BELOW; // Starting p
146 static const int ENTRIES; // Number of
147
148 };
149
150 } // namespace CLHEP
151
152 #include "CLHEP/Random/RandPoissonQ.icc"
153
154 #endif
155