| Geant4 Cross Reference |
1 // -*- C++ -*-
2 //
3 // -----------------------------------------------------------------------
4 // HEP Random
5 // --- RanshiEngine ---
6 // class header file
7 // -----------------------------------------------------------------------
8 //
9 //
10 // The algorithm for this random engine was taken from "F.Gutbrod, Comp.
11 // Phys. Comm. 87 (1995) 291-306".
12 //
13 // The algorithm can be imagined as a physical system as follows: Imagine
14 // 512 "black balls" each with their own unique spin, and positions char-
15 // acterized by disrete angles, where the spin is a 32-bit unsigned integer.
16 // A "red ball" collides based upon the angle determined by the last 8 bits
17 // of its spin, and the spin of the colliding ball is taken as the output
18 // random number. The spin of the colliding ball is replaced then with the
19 // left circular shift of the black ball's spin XOR'd with the red ball's
20 // spin. The black ball's old spin becomes the red ball's.
21 //
22 // To avoid the traps presented, two measures are taken: first, the red
23 // ball will oscillate between hitting the lower half of the buffer on one
24 // turn and the upper half on another; second, the red ball's spin is
25 // incremented by a counter of the number of random numbers produced.
26 //
27 // The result is scaled to a double precision floating point number to which
28 // is added another random double further scaled 2^(53-32) places to the
29 // right in order to ensure that the remaining bits of the result are not
30 // left empty due to the mere 32 bits representation used internally.
31
32 // =======================================================================
33 // Ken Smith - Created: 9th June 1998
34 // - Removed pow() from flat method: 21st Jul 1998
35 // - Added conversion operators: 6th Aug 1998
36 // Mark Fischler Methods put, get for instance save/restore 12/8/04
37 // Mark Fischler methods for anonymous save/restore 12/27/04
38 // =======================================================================
39
40 #ifndef HepRanshiEngine_h
41 #define HepRanshiEngine_h
42
43 #include "CLHEP/Random/RandomEngine.h"
44
45 namespace CLHEP {
46
47 /**
48 * @author
49 * @ingroup random
50 */
51 class RanshiEngine: public HepRandomEngine {
52
53 public:
54
55 RanshiEngine();
56 RanshiEngine(std::istream &is);
57 RanshiEngine(long seed);
58 RanshiEngine(int rowIndex, int colIndex);
59 virtual ~RanshiEngine();
60 // Constructors and destructor
61
62 double flat();
63 // Returns a pseudo random number between 0 and 1
64
65 void flatArray(const int size, double* vect);
66 // Fills the array "vect" of specified size with flat random values
67
68 void setSeed(long seed, int);
69 // Sets the state of the algorithm according to seed.
70
71 void setSeeds(const long* seeds, int);
72 // Sets the state of the algorithm according to the zero-terminated
73 // array of seeds.
74
75 void saveStatus(const char filename[] = "RanshiEngine.conf") const;
76 // Saves on named file the current engine status
77
78 void restoreStatus(const char filename[] = "RanshiEngine.conf");
79 // Reads from named file the last saved engine status
80 // and restores it.
81
82 void showStatus() const;
83 // Dumps the engine status on the screen
84
85 operator double(); // Returns same as flat()
86 operator float(); // flat value, without worrying about filling bits
87 operator unsigned int(); // 32-bit flat value, quickest of all
88
89 virtual std::ostream & put (std::ostream & os) const;
90 virtual std::istream & get (std::istream & is);
91 static std::string beginTag ( );
92 virtual std::istream & getState ( std::istream & is );
93
94 std::string name() const;
95 static std::string engineName() {return "RanshiEngine";}
96
97 std::vector<unsigned long> put () const;
98 bool get (const std::vector<unsigned long> & v);
99 bool getState (const std::vector<unsigned long> & v);
100
101 private:
102 enum {numBuff = 512};
103
104 unsigned int halfBuff, numFlats;
105 unsigned int buffer[numBuff];
106 unsigned int redSpin;
107
108 static const unsigned int VECTOR_STATE_SIZE = numBuff + 4;
109
110 }; // RanshiEngine
111
112 } // namespace CLHEP
113
114 #endif // HepRanshiEngine_h
115