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mt19937.c
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mt19937.c
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/*
A C-program for MT19937: Real number version
mt19937_generate_random_double() generates one pseudorandom
real number (double) which is uniformly distributed on
[0,1]-interval, for each call.
mt19937_seed_rng(seed) set initial values to the working area
of 624 words. Before mt19937_generate_random_double(),
mt19937_seed_rng(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.
Any feedback is very welcome. For any question, comments,
see http://www.math.keio.ac.jp/matumoto/emt.html or email
*/
#include "mt19937.h"
unsigned long mt[MT19937_N] = {0};
int mti = MT19937_N + 1;
/* initializing the array with a NONZERO seed */
void mt19937_seed_rng(unsigned long seed)
{
#ifdef DEBUG
fprintf(stderr, "Debug: Entering --> mt19937_seed_rng()\n");
#endif
/*
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 < MT19937_N; ++mti)
mt[mti] = (69069 * mt[mti - 1]) & 0xffffffff;
#ifdef DEBUG
fprintf(stderr, "Debug: Leaving --> mt19937_seed_rng()\n");
#endif
}
double mt19937_generate_random_double()
{
#ifdef DEBUG
fprintf(stderr, "Debug: Entering --> mt19937_generate_random_double()\n");
#endif
unsigned long y;
static unsigned long mag01[2] = {0x0, MT19937_MATRIX_A};
/* mag01[x] = x * MT19937_MATRIX_A for x=0,1 */
if (mti >= MT19937_N)
{
/* generate N words at one time */
int kk;
/* if mt19937_seed_rng() has not been called, a default initial seed is used */
if (mti == MT19937_N + 1)
mt19937_seed_rng(4357);
for (kk = 0;kk < MT19937_N - MT19937_M; ++kk)
{
y = (mt[kk] & MT19937_UPPER_MASK) | (mt[kk+1] & MT19937_LOWER_MASK);
mt[kk] = mt[kk + MT19937_M] ^ (y >> 1) ^ mag01[y & 0x1];
}
for (;kk < MT19937_N - 1; ++kk)
{
y = (mt[kk] & MT19937_UPPER_MASK) | (mt[kk + 1] & MT19937_LOWER_MASK);
mt[kk] = mt[kk + (MT19937_M - MT19937_N)] ^ (y >> 1) ^ mag01[y & 0x1];
}
y = (mt[MT19937_N - 1] & MT19937_UPPER_MASK) | (mt[0] & MT19937_LOWER_MASK);
mt[MT19937_N - 1] = mt[MT19937_M - 1] ^ (y >> 1) ^ mag01[y & 0x1];
mti = 0;
}
y = mt[mti++];
y ^= MT19937_SHIFT_U(y);
y ^= MT19937_SHIFT_S(y) & MT19937_MASK_B;
y ^= MT19937_SHIFT_T(y) & MT19937_MASK_C;
y ^= MT19937_SHIFT_L(y);
#ifdef DEBUG
fprintf(stderr, "Debug: Leaving --> mt19937_generate_random_double()\n");
#endif
return (double) y / (unsigned long) 0xffffffff;
}
unsigned long mt19937_generate_random_ulong()
{
#ifdef DEBUG
fprintf(stderr, "Debug: Entering --> mt19937_generate_random_ulong()\n");
#endif
unsigned long y;
static unsigned long mag01[2] = {0x0, MT19937_MATRIX_A};
/* mag01[x] = x * MT19937_MATRIX_A for x=0,1 */
if (mti >= MT19937_N)
{
/* generate N words at one time */
int kk;
/* if mt19937_seed_rng() has not been called, a default initial seed is used */
if (mti == MT19937_N + 1)
mt19937_seed_rng(4357);
for (kk = 0;kk < MT19937_N - MT19937_M; ++kk)
{
y = (mt[kk] & MT19937_UPPER_MASK) | (mt[kk+1] & MT19937_LOWER_MASK);
mt[kk] = mt[kk + MT19937_M] ^ (y >> 1) ^ mag01[y & 0x1];
}
for (;kk < MT19937_N - 1; ++kk)
{
y = (mt[kk] & MT19937_UPPER_MASK) | (mt[kk + 1] & MT19937_LOWER_MASK);
mt[kk] = mt[kk + (MT19937_M - MT19937_N)] ^ (y >> 1) ^ mag01[y & 0x1];
}
y = (mt[MT19937_N - 1] & MT19937_UPPER_MASK) | (mt[0] & MT19937_LOWER_MASK);
mt[MT19937_N - 1] = mt[MT19937_M - 1] ^ (y >> 1) ^ mag01[y & 0x1];
mti = 0;
}
y = mt[mti++];
y ^= MT19937_SHIFT_U(y);
y ^= MT19937_SHIFT_S(y) & MT19937_MASK_B;
y ^= MT19937_SHIFT_T(y) & MT19937_MASK_C;
y ^= MT19937_SHIFT_L(y);
#ifdef DEBUG
fprintf(stderr, "Debug: Leaving --> mt19937_generate_random_ulong()\n");
#endif
return y;
}