diff options
Diffstat (limited to 'gsl-1.9/rng/knuthran2.c')
-rw-r--r-- | gsl-1.9/rng/knuthran2.c | 103 |
1 files changed, 103 insertions, 0 deletions
diff --git a/gsl-1.9/rng/knuthran2.c b/gsl-1.9/rng/knuthran2.c new file mode 100644 index 0000000..30cd9d2 --- /dev/null +++ b/gsl-1.9/rng/knuthran2.c @@ -0,0 +1,103 @@ +/* rng/knuthran2.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 + * Page 108 + * + * This implementation copyright (C) 2001 Carlo Perassi + * and (C) 2003 Heiko Bauke. + */ + +#include <config.h> +#include <stdlib.h> +#include <gsl/gsl_rng.h> + +#include "schrage.c" + +#define AA1 271828183UL +#define AA2 1833324378UL /* = -314159269 mod (2 ^ 31 -1) */ +#define MM 0x7fffffffUL /* 2 ^ 31 - 1 */ +#define CEIL_SQRT_MM 46341UL /* sqrt(2 ^ 31 - 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 x0; + unsigned long int x1; +} +ran_state_t; + +static inline unsigned long int +ran_get (void *vstate) +{ + ran_state_t *state = (ran_state_t *) vstate; + + const unsigned long int xtmp = state->x1; + state->x1 = schrage_mult (AA1, state->x1, MM, CEIL_SQRT_MM) + + schrage_mult (AA2, state->x0, MM, CEIL_SQRT_MM); + + if (state->x1 >= MM) + state->x1 -= MM; + + state->x0 = xtmp; + + return state->x1; +} + +static double +ran_get_double (void *vstate) +{ + ran_state_t *state = (ran_state_t *) vstate; + + return ran_get (state) / 2147483647.0; +} + +static void +ran_set (void *vstate, unsigned long int s) +{ + ran_state_t *state = (ran_state_t *) vstate; + + if ((s % MM) == 0) + s = 1; /* default seed is 1 */ + + state->x0 = s % MM; + state->x1 = s % MM; + + return; +} + +static const gsl_rng_type ran_type = { + "knuthran2", /* name */ + MM - 1L, /* RAND_MAX */ + 0, /* RAND_MIN */ + sizeof (ran_state_t), + &ran_set, + &ran_get, + &ran_get_double +}; + +const gsl_rng_type *gsl_rng_knuthran2 = &ran_type; |