123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131 |
- /* rng/ran1.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"
- /* This is an implementation of the algorithm used in Numerical
- Recipe's ran1 generator. It is MINSTD with a 32-element
- shuffle-box. */
- static inline unsigned long int ran1_get (void *vstate);
- static double ran1_get_double (void *vstate);
- static void ran1_set (void *state, unsigned long int s);
- static const long int m = 2147483647, a = 16807, q = 127773, r = 2836;
- #define N_SHUFFLE 32
- #define N_DIV (1 + 2147483646/N_SHUFFLE)
- typedef struct
- {
- unsigned long int x;
- unsigned long int n;
- unsigned long int shuffle[N_SHUFFLE];
- }
- ran1_state_t;
- static inline unsigned long int
- ran1_get (void *vstate)
- {
- ran1_state_t *state = (ran1_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;
- }
- {
- unsigned long int j = state->n / N_DIV;
- state->n = state->shuffle[j];
- state->shuffle[j] = state->x;
- }
- return state->n;
- }
- static double
- ran1_get_double (void *vstate)
- {
- float x_max = 1 - 1.2e-7f ; /* Numerical Recipes version of 1-FLT_EPS */
- float x = ran1_get (vstate) / 2147483647.0f ;
-
- if (x > x_max)
- return x_max ;
-
- return x ;
- }
- static void
- ran1_set (void *vstate, unsigned long int s)
- {
- ran1_state_t *state = (ran1_state_t *) vstate;
- int i;
- if (s == 0)
- s = 1; /* default seed is 1 */
- for (i = 0; i < 8; i++)
- {
- long int h = s / q;
- long int t = a * (s - h * q) - h * r;
- if (t < 0)
- t += m;
- s = t;
- }
- for (i = N_SHUFFLE - 1; i >= 0; i--)
- {
- long int h = s / q;
- long int t = a * (s - h * q) - h * r;
- if (t < 0)
- t += m;
- s = t;
- state->shuffle[i] = s;
- }
- state->x = s;
- state->n = s;
- return;
- }
- static const gsl_rng_type ran1_type =
- {"ran1", /* name */
- 2147483646, /* RAND_MAX */
- 1, /* RAND_MIN */
- sizeof (ran1_state_t),
- &ran1_set,
- &ran1_get,
- &ran1_get_double};
- const gsl_rng_type *gsl_rng_ran1 = &ran1_type;
|