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Reference Guide
StdEngine.h
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1 // @(#)root/mathcore:$Id$
2 // Author: L. Moneta Tue Aug 4 2015
3 
4 /**********************************************************************
5  * *
6  * Copyright (c) 2015 LCG ROOT Math Team, CERN/PH-SFT *
7  * *
8  * *
9  **********************************************************************/
10 
11 // random engines based on ROOT
12 
13 #ifndef ROOT_Math_StdEngine
14 #define ROOT_Math_StdEngine
15 
16 #include <random>
17 #include <string>
18 
19 namespace ROOT {
20 
21  namespace Math {
22 
23 
24  class StdRandomEngine {};
25 
26  template<class Generator>
27  struct StdEngineType {
28  static const char * Name() { return "std_random_eng";}
29  };
30  template<>
31  struct StdEngineType<std::minstd_rand> {
32  static const char * Name() { return "std_minstd_rand";}
33  };
34  template<>
35  struct StdEngineType<std::mt19937> {
36  static const char * Name() { return "std_mt19937";}
37  };
38  template<>
39  struct StdEngineType<std::mt19937_64> {
40  static const char * Name() { return "std_mt19937_64";}
41  };
42  template<>
43  struct StdEngineType<std::ranlux24> {
44  static const char * Name() { return "std_ranlux24";}
45  };
46  template<>
47  struct StdEngineType<std::ranlux48> {
48  static const char * Name() { return "std_ranlux48";}
49  };
50  template<>
51  struct StdEngineType<std::knuth_b> {
52  static const char * Name() { return "std_knuth_b";}
53  };
54  template<>
55  struct StdEngineType<std::random_device> {
56  static const char * Name() { return "std_random_device";}
57  };
58 
59 
60  /**
61  @ingroup Random
62  Class to wrap engines fron the C++ standard random library in
63  the ROOT Random interface.
64  This casess is then by used by the generic TRandoGen class
65  to provide TRandom interrace generators for the C++ random generators.
66 
67  See for examples the TRandomMT64 and TRandomRanlux48 generators
68  which are typede's to TRandomGen instaniated with some
69  random engine from the C++ standard library.
70 
71  */
72 
73  template <class Generator>
74  class StdEngine {
75 
76 
77  public:
78 
80  typedef typename Generator::result_type Result_t;
81 
82  StdEngine() : fGen() {
83  fCONS = 1./fGen.max();
84  }
85 
86 
87  void SetSeed(Result_t seed) { fGen.seed(seed);}
88 
89  double Rndm() {
90  Result_t rndm = fGen(); // generate integer number according to the type
91  if (rndm != 0) return fCONS*rndm;
92  return Rndm();
93  }
94 
96  return fGen();
97  }
98 
99  double operator() () {
100  return Rndm();
101  }
102 
103  static const char * Name() {
105  }
106 
107  static uint64_t MaxInt() { return Generator::max(); }
108 
109 
110  private:
111  Generator fGen;
112  double fCONS; //! cached value of maximum integer value generated
113  };
114 
115 
116  extern template class StdEngine<std::mt19937_64>;
117  extern template class StdEngine<std::ranlux48>;
118 
119  } // end namespace Math
120 
121 } // end namespace ROOT
122 
123 
124 #endif /* ROOT_Math_StdEngine */
Returns the available number of logical cores.
Definition: StringConv.hxx:21
StdRandomEngine BaseType
Definition: StdEngine.h:79
static const char * Name()
Definition: StdEngine.h:103
static uint64_t MaxInt()
Definition: StdEngine.h:107
STL namespace.
static const char * Name()
Definition: StdEngine.h:28
Result_t IntRndm()
Definition: StdEngine.h:95
Class to wrap engines fron the C++ standard random library in the ROOT Random interface.
Definition: StdEngine.h:74
Namespace for new Math classes and functions.
void SetSeed(Result_t seed)
Definition: StdEngine.h:87
Generator::result_type Result_t
Definition: StdEngine.h:80