07871354 |
1 | /* -*-c-*- |
2 | * |
b817bfc6 |
3 | * $Id: fibrand.h,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
07871354 |
4 | * |
5 | * Fibonacci generator |
6 | * |
7 | * (c) 1999 Straylight/Edgeware |
8 | */ |
9 | |
10 | /*----- Licensing notice --------------------------------------------------* |
11 | * |
12 | * This file is part of Catacomb. |
13 | * |
14 | * Catacomb is free software; you can redistribute it and/or modify |
15 | * it under the terms of the GNU Library General Public License as |
16 | * published by the Free Software Foundation; either version 2 of the |
17 | * License, or (at your option) any later version. |
18 | * |
19 | * Catacomb is distributed in the hope that it will be useful, |
20 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
21 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
22 | * GNU Library General Public License for more details. |
23 | * |
24 | * You should have received a copy of the GNU Library General Public |
25 | * License along with Catacomb; if not, write to the Free |
26 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
27 | * MA 02111-1307, USA. |
28 | */ |
29 | |
07871354 |
30 | /*----- Notes on the Fibonacci generator ----------------------------------* |
31 | * |
32 | * The generator was originally suggested by G. J. Mitchell and D. P. Moore |
33 | * in 1957, and publicized by D. E. Knuth as Algorithm 3.2.2A in volume 2 of |
34 | * his work `The Art of Computer Programming'. The generator is simple: at |
35 | * each stage it emits %$x_n = (x_{n - 55} + x_{n - 24}) \bmod 2^{32}$%. The |
36 | * period is proven to be greater than %$2^{55}$%, and statistical properties |
37 | * appear to be good. |
38 | */ |
39 | |
40 | #ifndef CATACOMB_FIBRAND_H |
41 | #define CATACOMB_FIBRAND_H |
42 | |
43 | #ifdef __cplusplus |
44 | extern "C" { |
45 | #endif |
46 | |
47 | /*----- Header files ------------------------------------------------------*/ |
48 | |
49 | #include <mLib/bits.h> |
50 | |
51 | #ifndef CATACOMB_GRAND_H |
52 | # include "grand.h" |
53 | #endif |
54 | |
55 | /*----- Magic constants ---------------------------------------------------*/ |
56 | |
57 | #define FIB_SZ 55 |
58 | #define FIB_TAP 24 |
59 | |
60 | /*----- Data structures ---------------------------------------------------*/ |
61 | |
62 | typedef struct fibrand { |
63 | unsigned i; |
64 | uint32 x[FIB_SZ]; |
65 | } fibrand; |
66 | |
67 | /*----- Functions provided ------------------------------------------------*/ |
68 | |
69 | /* --- @fibrand_step@ --- * |
70 | * |
71 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
72 | * |
73 | * Returns: Next output from generator. |
74 | * |
75 | * Use: Steps the generator. Returns |
e8c3c91f |
76 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. |
07871354 |
77 | */ |
78 | |
79 | extern uint32 fibrand_step(fibrand */*f*/); |
80 | |
81 | /* --- @fibrand_seed@ --- * |
82 | * |
83 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
84 | * @grand *r@ = random number generator to extract words from |
85 | * |
86 | * Returns: --- |
87 | * |
88 | * Use: Initializes a Fibonacci generator using word outputs from the |
89 | * given random number source @r@. |
90 | */ |
91 | |
92 | extern void fibrand_seed(fibrand */*f*/, grand */*r*/); |
93 | |
94 | /* --- @fibrand_lcseed@ --- * |
95 | * |
96 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
97 | * @uint32 seed@ = seed value |
98 | * |
99 | * Returns: --- |
100 | * |
101 | * Use: Initializes a Fibonacci generator using outputs from the |
102 | * @lcrand@ generator seeded from @seed@. This is faster than |
103 | * using a generic @lcrand@-based generator and @fibrand_rseed@ |
104 | * because it uses raw outputs rather than uniformly distributed |
105 | * 32-bit words. |
106 | */ |
107 | |
108 | extern void fibrand_lcseed(fibrand */*f*/, uint32 /*seed*/); |
109 | |
110 | /* --- @fibrand_range@ --- * |
111 | * |
112 | * Arguments: @fibrand *f@ = pointer to Fibonacci generator context |
113 | * @uint32 m@ = limit |
114 | * |
115 | * Returns: A uniformly distributed pseudorandom integer in the interval |
116 | * %$[0, m)$%. |
117 | */ |
118 | |
119 | extern uint32 fibrand_range(fibrand */*f*/, uint32 /*m*/); |
120 | |
121 | /* --- @fibrand_create@ --- * |
122 | * |
123 | * Arguments: @uint32 seed@ = initial seed |
124 | * |
125 | * Returns: Pointer to a generic generator. |
126 | * |
127 | * Use: Constructs a generic generator interface over a Fibonacci |
128 | * generator. The generator is seeded using @fibrand_lcseed@. |
129 | */ |
130 | |
131 | extern grand *fibrand_create(uint32 /*seed*/); |
132 | |
133 | /*----- That's all, folks -------------------------------------------------*/ |
134 | |
135 | #ifdef __cplusplus |
136 | } |
137 | #endif |
138 | |
139 | #endif |