| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id: fibrand.h,v 1.3 2004/04/08 01:36:15 mdw Exp $ |
| 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 | |
| 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 |
| 76 | * %$x_{i - 24} + x_{i - 55} \bmod 2^{32}$%. |
| 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 |