| /* rng/coveyou.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 |
| * Section 3.2.2 |
| * |
| * This implementation copyright (C) 2001 Carlo Perassi |
| * and (C) 2003 Heiko Bauke. |
| * Carlo Perassi reorganized the code to use the rng framework of GSL. |
| */ |
| |
| #include <config.h> |
| #include <stdlib.h> |
| #include <gsl/gsl_rng.h> |
| |
| #define MM 0xffffffffUL /* 2 ^ 32 - 1 */ |
| |
| 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); |
| |
| 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; |
| |
| state->x = (state->x * (state->x + 1)) & MM; |
| |
| return state->x; |
| } |
| |
| static double |
| ran_get_double (void *vstate) |
| { |
| ran_state_t *state = (ran_state_t *) vstate; |
| |
| return ran_get (state) / 4294967296.0; |
| } |
| |
| static void |
| ran_set (void *vstate, unsigned long int s) |
| { |
| ran_state_t *state = (ran_state_t *) vstate; |
| |
| unsigned long int diff = ((s % 4UL) - 2UL) % MM; |
| |
| if (diff) |
| state->x = (s - diff) & MM; |
| else |
| state->x = s & MM; |
| |
| return; |
| } |
| |
| static const gsl_rng_type ran_type = { |
| "coveyou", /* name */ |
| MM-1, /* RAND_MAX */ |
| 2, /* RAND_MIN */ |
| sizeof (ran_state_t), |
| &ran_set, |
| &ran_get, |
| &ran_get_double |
| }; |
| |
| const gsl_rng_type *gsl_rng_coveyou = &ran_type; |