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/* rng/fishman20.c
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program 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
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/*
* This generator is taken from
*
* Donald E. Knuth
* The Art of Computer Programming
* Volume 2
* Third Edition
* Addison-Wesley
* Page 108
*
* It is called "Fishman"
*
* This implementation copyright (C) 2001 Carlo Perassi
* and (C) 2003 Heiko Bauke.
*/
#include <config.h>
#include <stdlib.h>
#include <gsl/gsl_rng.h>
static inline unsigned long int ran_get (void *vstate);
static double ran_get_double (void *vstate);
static void ran_set (void *state, unsigned long int s);
static const long int m = 2147483647, a = 48271, q = 44488, r = 3399;
typedef struct
{
unsigned long int x;
}
ran_state_t;
static inline unsigned long int
ran_get (void *vstate)
{
ran_state_t *state = (ran_state_t *) vstate;
const unsigned long int x = state->x;
const long int h = x / q;
const long int t = a * (x - h * q) - h * r;
if (t < 0)
{
state->x = t + m;
}
else
{
state->x = t;
}
return state->x;
}
static double
ran_get_double (void *vstate)
{
ran_state_t *state = (ran_state_t *) vstate;
return ran_get (state) / 2147483647.0;
}
static void
ran_set (void *vstate, unsigned long int s)
{
ran_state_t *state = (ran_state_t *) vstate;
if ((s%m) == 0)
s = 1; /* default seed is 1 */
state->x = s & m;
return;
}
static const gsl_rng_type ran_type = {
"fishman20", /* name */
2147483646, /* RAND_MAX */
1, /* RAND_MIN */
sizeof (ran_state_t),
&ran_set,
&ran_get,
&ran_get_double
};
const gsl_rng_type *gsl_rng_fishman20 = &ran_type;
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