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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 "gsl__config.h"
- #include <stdlib.h>
- #include "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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