An

algorithm to generate

random numbers. It is significantly

faster than your average

libc implementation and generates a more random

distribution of numbers. The

homepage can be found at http://www.math.keio.ac.jp/~matumoto/emt.html which has various

implementations in various languages, as well as more information on the

code and algorithms.

/* A C-program for MT19937: Integer version (1998/4/6) */
/* genrand() generates one pseudorandom unsigned integer (32bit) */
/* which is uniformly distributed among 0 to 2^32-1 for each */
/* call. sgenrand(seed) set initial values to the working area */
/* of 624 words. Before genrand(), sgenrand(seed) must be */
/* called once. (seed is any 32-bit integer except for 0). */
/* Coded by Takuji Nishimura, considering the suggestions by */
/* Topher Cooper and Marc Rieffel in July-Aug. 1997. */
/* This library is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library General Public */
/* License as published by the Free Software Foundation; either */
/* version 2 of the License, or (at your option) any later */
/* version. */
/* This library 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 Library General Public License for more details. */
/* You should have received a copy of the GNU Library General */
/* Public License along with this library; if not, write to the */
/* Free Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA */
/* 02111-1307 USA */
/* Copyright (C) 1997 Makoto Matsumoto and Takuji Nishimura. */
/* When you use this, send an email to: matumoto@math.keio.ac.jp */
/* with an appropriate reference to your work. */
/* REFERENCE */
/* M. Matsumoto and T. Nishimura, */
/* "Mersenne Twister: A 623-Dimensionally Equidistributed Uniform */
/* Pseudo-Random Number Generator", */
/* ACM Transactions on Modeling and Computer Simulation, */
/* Vol. 8, No. 1, January 1998, pp 3--30. */
#include<stdio.h>
/* Period parameters */
#define N 624
#define M 397
#define MATRIX_A 0x9908b0df /* constant vector a */
#define UPPER_MASK 0x80000000 /* most significant w-r bits */
#define LOWER_MASK 0x7fffffff /* least significant r bits */
/* Tempering parameters */
#define TEMPERING_MASK_B 0x9d2c5680
#define TEMPERING_MASK_C 0xefc60000
#define TEMPERING_SHIFT_U(y) (y >> 11)
#define TEMPERING_SHIFT_S(y) (y < 7)
#define TEMPERING_SHIFT_T(y) (y < 15)
#define TEMPERING_SHIFT_L(y) (y >> 18)
static unsigned long mt[N]; /* the array for the state vector */
static int mti=N+1; /* mti==N+1 means mt[N] is not initialized */
/* initializing the array with a NONZERO seed */
void
sgenrand(seed)
unsigned long seed;
{
/* setting initial seeds to mt[N] using */
/* the generator Line 25 of Table 1 in */
/* KNUTH 1981, The Art of Computer Programming */
/* Vol. 2 (2nd Ed.), pp102 */
mt[0]= seed & 0xffffffff;
for (mti=1; mti= N) { /* generate N words at one time */
int kk;
if (mti == N+1) /* if sgenrand() has not been called, */
sgenrand(4357); /* a default initial seed is used */
for (kk=0;kk> 1) ^ mag01y & 0x1;
}
for (;kk> 1) ^ mag01[y & 0x1];
}
y = (mt[N-1]&UPPER_MASK)|(mt[0]&LOWER_MASK);
mt[N-1] = mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
mti = 0;
}
y = mt[mti++];
y ^= TEMPERING_SHIFT_U(y);
y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
y ^= TEMPERING_SHIFT_L(y);
return y;
}
/* this main() outputs first 1000 generated numbers */
main()
{
int j;
sgenrand(4357); /* any nonzero integer can be used as a seed */
for (j=0; j<1000; j++) {
printf("%10lu ", genrand());
if (j%8==7) printf("\n");
}
printf("\n");
}