From 2e7e9b73a0e7c1a00c43a80d318dd40a45108491 Mon Sep 17 00:00:00 2001 From: david Date: Mon, 5 Aug 2002 18:43:28 +0000 Subject: [PATCH] Change from Norman Vine to add new random-number algorithm. --- simgear/math/sg_random.c | 137 +++++++++++++++++++++++++++++++-------- 1 file changed, 110 insertions(+), 27 deletions(-) diff --git a/simgear/math/sg_random.c b/simgear/math/sg_random.c index ec103f13..fa3f213d 100644 --- a/simgear/math/sg_random.c +++ b/simgear/math/sg_random.c @@ -22,59 +22,142 @@ // $Id$ +/* + A C-program for MT19937, with initialization improved 2002/2/10. + Coded by Takuji Nishimura and Makoto Matsumoto. + This is a faster version by taking Shawn Cokus's optimization, + Matthe Bellew's simplification, Isaku Wada's real version. + + Before using, initialize the state by using init_genrand(seed) + or init_by_array(init_key, key_length). + + Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura, + All rights reserved. + + Redistribution and use in source and binary forms, with or without + modification, are permitted provided that the following conditions + are met: + + 1. Redistributions of source code must retain the above copyright + notice, this list of conditions and the following disclaimer. + + 2. Redistributions in binary form must reproduce the above copyright + notice, this list of conditions and the following disclaimer in the + documentation and/or other materials provided with the distribution. + + 3. The names of its contributors may not be used to endorse or promote + products derived from this software without specific prior written + permission. + + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR + CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, + PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR + PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING + NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + + + Any feedback is very welcome. + http://www.math.keio.ac.jp/matumoto/emt.html + email: matumoto@math.keio.ac.jp +*/ + #ifdef HAVE_CONFIG_H # include #endif #include -#include // for random(), srandom(), drand48() +#include // for random(), srandom() #include // for time() to seed srandom() #include "sg_random.h" -#ifdef __SUNPRO_CC - extern "C" { - long int random(); - void srandom(unsigned int seed); +/* Period parameters */ +#define N 624 +#define M 397 +#define MATRIX_A 0x9908b0dfUL /* constant vector a */ +#define UMASK 0x80000000UL /* most significant w-r bits */ +#define LMASK 0x7fffffffUL /* least significant r bits */ +#define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) ) +#define TWIST(u,v) ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL)) + +static unsigned long state[N]; /* the array for the state vector */ +static int left = 1; +static int initf = 0; +static unsigned long *next; + +/* initializes state[N] with a seed */ +void init_genrand(unsigned long s) +{ + int j; + state[0]= s & 0xffffffffUL; + for (j=1; j> 30)) + j); + /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */ + /* In the previous versions, MSBs of the seed affect */ + /* only MSBs of the array state[]. */ + /* 2002/01/09 modified by Makoto Matsumoto */ + state[j] &= 0xffffffffUL; /* for >32 bit machines */ } -#endif + left = 1; initf = 1; +} + +static void next_state(void) +{ + unsigned long *p=state; + int j; + + /* if init_genrand() has not been called, */ + /* a default initial seed is used */ + if (initf==0) init_genrand(5489UL); + + left = N; + next = state; + + for (j=N-M+1; --j; p++) + *p = p[M] ^ TWIST(p[0], p[1]); + for (j=M; --j; p++) + *p = p[M-N] ^ TWIST(p[0], p[1]); + + *p = p[M-N] ^ TWIST(p[0], state[0]); +} // Seed the random number generater with time() so we don't see the // same sequence every time void sg_srandom_time() { -#ifdef HAVE_DRAND48 - srand48(time(NULL) + getpid()); -#elif defined( HAVE_RANDOM ) - srandom(time(NULL)); -#else - srand(time(NULL)); -#endif + init_genrand(time(NULL)); } // Seed the random number generater with your own seed so can set up // repeatable randomization. void sg_srandom( unsigned int seed ) { -#ifdef HAVE_DRAND48 - srand48( seed ); -#elif defined( HAVE_RANDOM ) - srandom( seed ); -#else - srand( seed ); -#endif + init_genrand( seed ); } // return a random number between [0.0, 1.0) double sg_random() { -#ifdef HAVE_DRAND48 - return(drand48()); -#elif defined( HAVE_RANDOM ) - return(random() / (double)RAND_MAX); -#else - return(rand() / (double)RAND_MAX); -#endif + unsigned long y; + + if (--left == 0) + next_state(); + y = *next++; + + /* Tempering */ + y ^= (y >> 11); + y ^= (y << 7) & 0x9d2c5680UL; + y ^= (y << 15) & 0xefc60000UL; + y ^= (y >> 18); + + return (double)y * (1.0/4294967295.0); + /* divided by 2^32-1 */ } -- 2.39.5