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- /* rng/ran3.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 Knuths's
- subtractive generator, with the Numerical Recipe's ran3 paramters.
- It is a subtractive lagged fibonnaci generator. */
- static inline unsigned long int ran3_get (void *vstate);
- static double ran3_get_double (void *vstate);
- static void ran3_set (void *state, unsigned long int s);
- #define M_BIG 1000000000
- #define M_SEED 161803398
- typedef struct
- {
- unsigned int x;
- unsigned int y;
- unsigned long int buffer[56];
- }
- ran3_state_t;
- static inline unsigned long int
- ran3_get (void *vstate)
- {
- ran3_state_t *state = (ran3_state_t *) vstate;
- long int j;
- state->x++;
- if (state->x == 56)
- state->x = 1;
- state->y++;
- if (state->y == 56)
- state->y = 1;
- j = state->buffer[state->x] - state->buffer[state->y];
- if (j < 0)
- j += M_BIG;
- state->buffer[state->x] = j;
- return j;
- }
- static double
- ran3_get_double (void *vstate)
- {
- return ran3_get (vstate) / (double) M_BIG ;
- }
- static void
- ran3_set (void *vstate, unsigned long int s)
- {
- ran3_state_t *state = (ran3_state_t *) vstate;
- int i, i1;
- long int j, k;
- if (s == 0)
- s = 1; /* default seed is 1 */
- j = (M_SEED - s) % M_BIG;
- /* the zeroth element is never used, but we initialize it for
- consistency between states */
- state->buffer[0] = 0;
- state->buffer[55] = j;
- k = 1;
- for (i = 1; i < 55; i++)
- {
- int n = (21 * i) % 55;
- state->buffer[n] = k;
- k = j - k;
- if (k < 0)
- k += M_BIG;
- j = state->buffer[n];
- }
- for (i1 = 0; i1 < 4; i1++)
- {
- for (i = 1; i < 56; i++)
- {
- long int t = state->buffer[i] - state->buffer[1 + (i + 30) % 55];
- if (t < 0)
- t += M_BIG;
- state->buffer[i] = t;
- }
- }
- state->x = 0;
- state->y = 31;
- return;
- }
- static const gsl_rng_type ran3_type =
- {"ran3", /* name */
- M_BIG, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (ran3_state_t),
- &ran3_set,
- &ran3_get,
- &ran3_get_double};
- const gsl_rng_type *gsl_rng_ran3 = &ran3_type;
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