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/* rng/zuf.c
*
* Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 James Theiler, Brian Gough
*
* 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 3 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.
*/
#include <config.h>
#include <stdlib.h>
#include <gsl/gsl_rng.h>
/* It is crucial that m == n-273 mod 607 at all times;
For speed of execution, however, this is never enforced.
Instead is is set in the initializer: note 607-273=334
Note also that the state.u[607] is not initialized */
static inline unsigned long int zuf_get (void *vstate);
static double zuf_get_double (void *vstate);
static void zuf_set (void *state, unsigned long int s);
static const unsigned long int zuf_randmax = 16777216; /* 2^24 */
typedef struct
{
int n;
unsigned long int u[607];
}
zuf_state_t;
/* The zufall package was implemented with float's, which is to say 24
bits of precision. Since I'm using long's instead, my RANDMAX
reflects this. */
static inline unsigned long int
zuf_get (void *vstate)
{
zuf_state_t *state = (zuf_state_t *) vstate;
const int n = state->n;
const int m = (n - 273 + 607) % 607;
unsigned long int t = state->u[n] + state->u[m];
while (t > zuf_randmax)
t -= zuf_randmax;
state->u[n] = t;
if (n == 606)
{
state->n = 0;
}
else
{
state->n = n + 1;
}
return t;
}
static double
zuf_get_double (void *vstate)
{
return zuf_get (vstate) / 16777216.0 ;
}
static void
zuf_set (void *vstate, unsigned long int s)
{
/* A very elaborate seeding procedure is provided with the
zufall package; this is virtually a copy of that procedure */
/* Initialized data */
long int kl = 9373;
long int ij = 1802;
/* Local variables */
long int i, j, k, l, m;
double x, y;
long int ii, jj;
zuf_state_t *state = (zuf_state_t *) vstate;
state->n = 0;
/* generates initial seed buffer by linear congruential */
/* method. Taken from Marsaglia, FSU report FSU-SCRI-87-50 */
/* variable seed should be 0 < seed <31328 */
if (s == 0)
s = 1802; /* default seed is 1802 */
ij = s;
i = ij / 177 % 177 + 2;
j = ij % 177 + 2;
k = kl / 169 % 178 + 1;
l = kl % 169;
for (ii = 0; ii < 607; ++ii)
{
x = 0.0;
y = 0.5;
/* 24 bits?? */
for (jj = 1; jj <= 24; ++jj)
{
m = i * j % 179 * k % 179;
i = j;
j = k;
k = m;
l = (l * 53 + 1) % 169;
if (l * m % 64 >= 32)
{
x += y;
}
y *= 0.5;
}
state->u[ii] = (unsigned long int) (x * zuf_randmax);
}
}
static const gsl_rng_type zuf_type =
{"zuf", /* name */
0x00ffffffUL, /* RAND_MAX */
0, /* RAND_MIN */
sizeof (zuf_state_t),
&zuf_set,
&zuf_get,
&zuf_get_double};
const gsl_rng_type *gsl_rng_zuf = &zuf_type;
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