mt.c

/*
 * 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.
 */

#include <stdio.h>

/* Period parameters */
#define MT_N 624
#define MT_M 397
#define MT_MATRIX_A 0x9908b0dfUL        
#define MT_UPPER_MASK 0x80000000UL      
#define MT_LOWER_MASK 0x7fffffffUL      
static unsigned long mt[MT_N];  
static int mti = MT_N + 1;      
static void init_genrand(unsigned long s)
{
    mt[0] = s & 0xffffffffUL;
    for (mti = 1; mti < MT_N; mti++) {
        mt[mti] = (1812433253UL * (mt[mti - 1] ^ (mt[mti - 1] >> 30)) + mti);
        /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
        /* In the previous versions, MSBs of the seed affect   */
        /* only MSBs of the array mt[].                        */
        /* 2002/01/09 modified by Makoto Matsumoto             */
        mt[mti] &= 0xffffffffUL;
        /* for >32 bit machines */
    }
}

static unsigned long genrand_int32(void)
{
    unsigned long y;
    static unsigned long mag01[2] = { 0x0UL, MT_MATRIX_A };
    /* mag01[x] = x * MT_MATRIX_A  for x=0,1 */

    if (mti >= MT_N) {          /* generate MT_N words at one time */
        int kk;

        if (mti == MT_N + 1)    /* if init_genrand() has not been called, */
            init_genrand(5489UL);       /* a default initial seed is used */

        for (kk = 0; kk < MT_N - MT_M; kk++) {
            y = (mt[kk] & MT_UPPER_MASK) | (mt[kk + 1] & MT_LOWER_MASK);
            mt[kk] = mt[kk + MT_M] ^ (y >> 1) ^ mag01[y & 0x1UL];
        }
        for (; kk < MT_N - 1; kk++) {
            y = (mt[kk] & MT_UPPER_MASK) | (mt[kk + 1] & MT_LOWER_MASK);
            mt[kk] = mt[kk + (MT_M - MT_N)] ^ (y >> 1) ^ mag01[y & 0x1UL];
        }
        y = (mt[MT_N - 1] & MT_UPPER_MASK) | (mt[0] & MT_LOWER_MASK);
        mt[MT_N - 1] = mt[MT_M - 1] ^ (y >> 1) ^ mag01[y & 0x1UL];

        mti = 0;
    }

    y = mt[mti++];

    /* Tempering */
    y ^= (y >> 11);
    y ^= (y << 7) & 0x9d2c5680UL;
    y ^= (y << 15) & 0xefc60000UL;
    y ^= (y >> 18);

    return y;
}

static double genrand_res53(void)
{
    unsigned long a = genrand_int32() >> 5, b = genrand_int32() >> 6;
    return (1.0 * a * 67108864.0 + b) * (1.0 / 9007199254740992.0);
}

#undef MT_N
#undef MT_M
#undef MT_MATRIX_A
#undef MT_UPPER_MASK
#undef MT_LOWER_MASK

/*
 * The remainder of this file is
 * Copyright (C) 2010-2011 Nicolas Limare <nicolas.limare@cmla.ens-cachan.fr>
 * and distributed under the same conditions as the original file.
 */

#include <time.h>

/* get the high-precision timer specified by POSIX.1-2001 if available */
#if defined(unix) || defined(__unix__) || defined(__unix)
#include <unistd.h>
#if defined(_POSIX_VERSION)
#if (_POSIX_VERSION >= 200112L)
#include <sys/time.h>
#define USE_GETTIMEOFDAY
#endif
#endif
#endif

/* ensure consistency */
#include "mt.h"

/* string tag inserted into the binary */
static char mt_tag[] = "using mt " MT_VERSION;
char *mt_info(void)
{
    return mt_tag;
}

void mt_init(unsigned long s)
{
    init_genrand(s);
    return;
}

void mt_init_auto(void)
{
    unsigned long int seed;

    /*
     * the basic (weak) initialization
     * uses the current time, in seconds
     */
    seed = (unsigned long int) time(NULL);

#if defined(USE_GETTIMEOFDAY)
    /* gettimeofday() provides a millisecond time */
    {
        struct timeval tp;
        (void) gettimeofday(&tp, NULL);

        seed *= 1000000;
        seed += tp.tv_usec;
    }
#endif

    mt_init(seed);
    return;
}

double mt_drand53(void)
{
    return genrand_res53();
}