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- /* 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 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.
- */
- /*
- * 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 "gsl__config.h"
- #include <stdlib.h>
- #include "gsl_rng.h"
- #include "gsl_rng__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;
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