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///Copyright Paul Reiche, Fred Ford. 1992-2002
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*/
/****************************************************************************
* FILE: random.c
* DESC: a library of random number generators for general purpose use.
*
* References:
* "Random Number Generators: Good ones are hard to find" S.K.Park & K.W.Miller
* Communications of the ACM, Vol31 Number 10, October 1988, Pp 1192-1201
*
* HISTORY: Created 1/23/1989
* LAST CHANGED:
*
* Copyright (c) 1989, Robert Leyland and Fred Ford
****************************************************************************/
/* ----------------------------INCLUDES----------------------------------- */
#include "mthintrn.h" /* get the externs for error checking */
/* ----------------------------DEFINES------------------------------------ */
/* constants for licongruential random number generator from CACM article
referenced above */
#define A 16807 /* a relatively prime number -- also M div Q */
#define M 2147483647L /* 0xFFFFFFFF / 2 */
#define Q 127773L /* M div A */
#define R 2836 /* M mod A */
/* ----------------------------STATIC DATA-------------------------------- */
static DWORD seed = 12345L; /* random number seed */
/* ----------------------------CODE--------------------------------------- */
/*****************************************************************************
* FUNC: DWORD TFB_Random()
*
* DESC: random number generator
*
* NOTES:
*
* HISTORY: Created By Robert leyland
*
*****************************************************************************/
DWORD
TFB_Random (void)
{
seed = A * (seed % Q) - R * (seed / Q);
if (seed > M)
return (seed -= M);
else if (seed)
return (seed);
else
return (seed = 1L);
}
/*****************************************************************************
* FUNC: DWORD TFB_SeedRandom(DWORD l)
*
* DESC: set the seed for the random number generator to parameter "l", and
* return the value of the previously active seed, to allow for multiple
* random number streams.
*
* NOTES: if the seed is not valid it will be coerced into a valid range
*
* HISTORY: Created By Robert leyland
*
*****************************************************************************/
DWORD
TFB_SeedRandom (DWORD new_seed)
{
DWORD old_seed;
/* coerce the seed to be in the range 1..M */
if (new_seed == 0L) /* 0 becomes 1 */
new_seed = 1;
else if (new_seed > M) /* and less than M */
new_seed -= M;
old_seed = seed;
seed = new_seed;
return (old_seed);
}
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