| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * $Id$ |
| 4 | * |
| 5 | * Simple linear congruential generator |
| 6 | * |
| 7 | * (c) 1999 Straylight/Edgeware |
| 8 | * (c) 2000 Mark Wooding |
| 9 | */ |
| 10 | |
| 11 | /*----- Licensing notice --------------------------------------------------* |
| 12 | * |
| 13 | * Copyright (c) 2000 Mark Wooding |
| 14 | * All rights reserved. |
| 15 | * |
| 16 | * Redistribution and use in source and binary forms, with or without |
| 17 | * modification, are permitted provided that the following conditions are |
| 18 | * met: |
| 19 | * |
| 20 | * 1. Redistributions of source code must retain the above copyright |
| 21 | * notice, this list of conditions and the following disclaimer. |
| 22 | * |
| 23 | * 2, Redistributions in binary form must reproduce the above copyright |
| 24 | * notice, this list of conditions and the following disclaimer in the |
| 25 | * documentation and/or other materials provided with the distribution. |
| 26 | * |
| 27 | * 3. The name of the authors may not be used to endorse or promote |
| 28 | * products derived from this software without specific prior written |
| 29 | * permission. |
| 30 | * |
| 31 | * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 32 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 33 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN |
| 34 | * NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| 35 | * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| 36 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| 37 | * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| 38 | * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| 39 | * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
| 40 | * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 41 | * POSSIBILITY OF SUCH DAMAGE. |
| 42 | * |
| 43 | * Instead of accepting the above terms, you may redistribute and/or modify |
| 44 | * this software under the terms of either the GNU General Public License, |
| 45 | * or the GNU Library General Public License, published by the Free |
| 46 | * Software Foundation; either version 2 of the License, or (at your |
| 47 | * option) any later version. |
| 48 | */ |
| 49 | |
| 50 | /*----- Revision history --------------------------------------------------* |
| 51 | * |
| 52 | * $Log: lcrand.h,v $ |
| 53 | * Revision 1.2 2000/07/02 15:21:20 mdw |
| 54 | * Fix licence text. |
| 55 | * |
| 56 | * Revision 1.1 2000/05/21 11:28:30 mdw |
| 57 | * Initial check-in. |
| 58 | * |
| 59 | * --- Past lives (Catacomb) --- * |
| 60 | * |
| 61 | * Revision 1.1 1999/12/10 23:15:27 mdw |
| 62 | * Noncryptographic random number generator. |
| 63 | * |
| 64 | */ |
| 65 | |
| 66 | /*----- Notes on the linear congruential generator ------------------------* |
| 67 | * |
| 68 | * This pseudorandom number generator is simple, but has absolutely no |
| 69 | * cryptographic strength whatever. It may be used whenever random numbers |
| 70 | * are required but cryptographic strength is not, for example when |
| 71 | * generating numbers for use in primality tests. To be honest, it's not |
| 72 | * even particularly fast, although a certain amount of effort has been |
| 73 | * expended on making it better than awfully slow. To put things in |
| 74 | * perspective, it can't quite spit bytes out as fast as OFB DES. (Then |
| 75 | * again, bytes aren't its natural output format.) Its main use is probably |
| 76 | * seeding a Fibonacci generator. |
| 77 | * |
| 78 | * There exists a fixed-point input @LCRAND_FIXEDPT@ -- when fed to the |
| 79 | * generator it comes straight back out again. All other inputs less than |
| 80 | * the modulus are part of the same sequence of period %$p - 1$%. |
| 81 | * |
| 82 | * The generator has been tested for its statistical properties. George |
| 83 | * Marsaglia's Diehard tests give it a reasonably clean bill of health. |
| 84 | * |
| 85 | * The modulus %$p$% is chosen as the largest prime number less than |
| 86 | * %$2^{32}$%. The multiplier %$a$% and additive constant %$c$% are based on |
| 87 | * the decimal expansions of %$\pi$% and %$e$%, with the additional |
| 88 | * restriction that the multiplier must be a primitive element modulo %$p$%. |
| 89 | * The fixed point value is determined as %$c / (1 - a) \bmod p$%. |
| 90 | */ |
| 91 | |
| 92 | #ifndef LCRAND_H |
| 93 | #define LCRAND_H |
| 94 | |
| 95 | #ifdef __cplusplus |
| 96 | extern "C" { |
| 97 | #endif |
| 98 | |
| 99 | /*----- Header files ------------------------------------------------------*/ |
| 100 | |
| 101 | #ifndef BITS_H |
| 102 | # include "bits.h" |
| 103 | #endif |
| 104 | |
| 105 | /*----- Constants ---------------------------------------------------------*/ |
| 106 | |
| 107 | #define LCRAND_P 4294967291u /* Modulus for the generator */ |
| 108 | #define LCRAND_A 314159265u /* Multiplier (primitive mod @p@) */ |
| 109 | #define LCRAND_C 271828183u /* Additive constant */ |
| 110 | |
| 111 | #define LCRAND_FIXEDPT 3223959250u /* Fixed point (only bad input) */ |
| 112 | |
| 113 | /*----- Functions provided ------------------------------------------------*/ |
| 114 | |
| 115 | /* --- @lcrand@ --- * |
| 116 | * |
| 117 | * Arguments: @uint32 x@ = seed value |
| 118 | * |
| 119 | * Returns: New state of the generator. |
| 120 | * |
| 121 | * Use: Steps the generator. Returns %$ax + c \bmod p$%. |
| 122 | */ |
| 123 | |
| 124 | extern uint32 lcrand(uint32 /*x*/); |
| 125 | |
| 126 | /* --- @lcrand_range@ --- * |
| 127 | * |
| 128 | * Arguments: @uint32 *x@ = pointer to seed value (updated) |
| 129 | * @uint32 m@ = limit allowable |
| 130 | * |
| 131 | * Returns: A uniformly distributed pseudorandom integer in the interval |
| 132 | * %$[0, m)$%. |
| 133 | */ |
| 134 | |
| 135 | extern uint32 lcrand_range(uint32 */*x*/, uint32 /*m*/); |
| 136 | |
| 137 | /*----- That's all, folks -------------------------------------------------*/ |
| 138 | |
| 139 | #ifdef __cplusplus |
| 140 | } |
| 141 | #endif |
| 142 | |
| 143 | #endif |