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/* This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 3 of the
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License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details. You should have received
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a copy of the GNU General Public License along with this library; if
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not, write to the Free Software Foundation, Inc., 51 Franklin Street,
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Fifth Floor, Boston, MA 02110-1301, USA.
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Original implementation was copyright (C) 1997 Makoto Matsumoto and
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Takuji Nishimura. Coded by Takuji Nishimura, considering the
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suggestions by Topher Cooper and Marc Rieffel in July-Aug. 1997, "A
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C-program for MT19937: Integer version (1998/4/6)"
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This implementation copyright (C) 1998 Brian Gough. I reorganized
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the code to use the module framework of GSL. The license on this
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implementation was changed from LGPL to GPL, following paragraph 3
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of the LGPL, version 2.
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Update:
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The seeding procedure has been updated to match the 10/99 release
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of MT19937.
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Update:
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The seeding procedure has been updated again to match the 2002
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release of MT19937
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The original code included the comment: "When you use this, send an
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email to: matumoto@math.keio.ac.jp with an appropriate reference to
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your work".
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Makoto Matsumoto has a web page with more information about the
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generator, http://www.math.keio.ac.jp/~matumoto/emt.html.
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The paper below has details of the algorithm.
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From: Makoto Matsumoto and Takuji Nishimura, "Mersenne Twister: A
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623-dimensionally equidistributerd uniform pseudorandom number
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generator". ACM Transactions on Modeling and Computer Simulation,
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Vol. 8, No. 1 (Jan. 1998), Pages 3-30
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You can obtain the paper directly from Makoto Matsumoto's web page.
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The period of this generator is 2^{19937} - 1.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <gsl/gsl_rng.h>
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static inline unsigned long int mt_get (void *vstate);
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static double mt_get_double (void *vstate);
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static void mt_set (void *state, unsigned long int s);
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#define N 624 /* Period parameters */
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#define M 397
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/* most significant w-r bits */
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static const unsigned long UPPER_MASK = 0x80000000UL;
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/* least significant r bits */
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static const unsigned long LOWER_MASK = 0x7fffffffUL;
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typedef struct
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{
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unsigned long mt[N];
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int mti;
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}
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mt_state_t;
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static inline unsigned long
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mt_get (void *vstate)
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{
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mt_state_t *state = (mt_state_t *) vstate;
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unsigned long k ;
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unsigned long int *const mt = state->mt;
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#define MAGIC(y) (((y)&0x1) ? 0x9908b0dfUL : 0)
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if (state->mti >= N)
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{ /* generate N words at one time */
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int kk;
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for (kk = 0; kk < N - M; kk++)
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{
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unsigned long y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
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mt[kk] = mt[kk + M] ^ (y >> 1) ^ MAGIC(y);
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}
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for (; kk < N - 1; kk++)
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{
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unsigned long y = (mt[kk] & UPPER_MASK) | (mt[kk + 1] & LOWER_MASK);
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mt[kk] = mt[kk + (M - N)] ^ (y >> 1) ^ MAGIC(y);
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}
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{
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unsigned long y = (mt[N - 1] & UPPER_MASK) | (mt[0] & LOWER_MASK);
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mt[N - 1] = mt[M - 1] ^ (y >> 1) ^ MAGIC(y);
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}
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state->mti = 0;
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}
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/* Tempering */
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k = mt[state->mti];
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k ^= (k >> 11);
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k ^= (k << 7) & 0x9d2c5680UL;
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k ^= (k << 15) & 0xefc60000UL;
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k ^= (k >> 18);
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state->mti++;
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return k;
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}
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static double
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mt_get_double (void * vstate)
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{
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return mt_get (vstate) / 4294967296.0 ;
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}
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static void
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mt_set (void *vstate, unsigned long int s)
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{
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mt_state_t *state = (mt_state_t *) vstate;
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int i;
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if (s == 0)
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s = 4357; /* the default seed is 4357 */
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state->mt[0]= s & 0xffffffffUL;
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for (i = 1; i < N; i++)
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{
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/* See Knuth's "Art of Computer Programming" Vol. 2, 3rd
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Ed. p.106 for multiplier. */
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state->mt[i] =
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(1812433253UL * (state->mt[i-1] ^ (state->mt[i-1] >> 30)) + i);
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state->mt[i] &= 0xffffffffUL;
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}
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state->mti = i;
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}
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static void
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mt_1999_set (void *vstate, unsigned long int s)
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{
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mt_state_t *state = (mt_state_t *) vstate;
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int i;
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if (s == 0)
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s = 4357; /* the default seed is 4357 */
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/* This is the October 1999 version of the seeding procedure. It
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was updated by the original developers to avoid the periodicity
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in the simple congruence originally used.
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Note that an ANSI-C unsigned long integer arithmetic is
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automatically modulo 2^32 (or a higher power of two), so we can
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safely ignore overflow. */
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#define LCG(x) ((69069 * x) + 1) &0xffffffffUL
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for (i = 0; i < N; i++)
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{
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state->mt[i] = s & 0xffff0000UL;
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s = LCG(s);
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state->mt[i] |= (s &0xffff0000UL) >> 16;
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s = LCG(s);
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}
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state->mti = i;
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}
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/* This is the original version of the seeding procedure, no longer
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used but available for compatibility with the original MT19937. */
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static void
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mt_1998_set (void *vstate, unsigned long int s)
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{
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mt_state_t *state = (mt_state_t *) vstate;
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int i;
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if (s == 0)
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s = 4357; /* the default seed is 4357 */
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state->mt[0] = s & 0xffffffffUL;
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#define LCG1998(n) ((69069 * n) & 0xffffffffUL)
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for (i = 1; i < N; i++)
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state->mt[i] = LCG1998 (state->mt[i - 1]);
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state->mti = i;
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}
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static const gsl_rng_type mt_type =
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{"mt19937", /* name */
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0xffffffffUL, /* RAND_MAX */
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0, /* RAND_MIN */
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sizeof (mt_state_t),
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&mt_set,
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&mt_get,
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&mt_get_double};
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static const gsl_rng_type mt_1999_type =
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{"mt19937_1999", /* name */
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0xffffffffUL, /* RAND_MAX */
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0, /* RAND_MIN */
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sizeof (mt_state_t),
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&mt_1999_set,
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&mt_get,
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&mt_get_double};
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static const gsl_rng_type mt_1998_type =
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{"mt19937_1998", /* name */
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0xffffffffUL, /* RAND_MAX */
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0, /* RAND_MIN */
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sizeof (mt_state_t),
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&mt_1998_set,
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&mt_get,
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&mt_get_double};
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const gsl_rng_type *gsl_rng_mt19937 = &mt_type;
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const gsl_rng_type *gsl_rng_mt19937_1999 = &mt_1999_type;
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const gsl_rng_type *gsl_rng_mt19937_1998 = &mt_1998_type;
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/* MT19937 is the default generator, so define that here too */
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const gsl_rng_type *gsl_rng_default = &mt_type;
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unsigned long int gsl_rng_default_seed = 0;
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