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/* rng/knuthran2.c
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or (at
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* your option) any later version.
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*
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* This program is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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/*
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* This generator is taken from
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*
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* Donald E. Knuth
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* The Art of Computer Programming
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* Volume 2
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* Third Edition
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* Addison-Wesley
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* Page 108
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*
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* This implementation copyright (C) 2001 Carlo Perassi
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* and (C) 2003 Heiko Bauke.
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*/
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#include <config.h>
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#include <stdlib.h>
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#include <gsl/gsl_rng.h>
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#include "schrage.c"
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#define AA1 271828183UL
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#define AA2 1833324378UL /* = -314159269 mod (2 ^ 31 -1) */
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#define MM 0x7fffffffUL /* 2 ^ 31 - 1 */
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#define CEIL_SQRT_MM 46341UL /* sqrt(2 ^ 31 - 1) */
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static inline unsigned long int ran_get (void *vstate);
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static double ran_get_double (void *vstate);
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static void ran_set (void *state, unsigned long int s);
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typedef struct
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{
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unsigned long int x0;
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unsigned long int x1;
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}
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ran_state_t;
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static inline unsigned long int
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ran_get (void *vstate)
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{
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ran_state_t *state = (ran_state_t *) vstate;
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const unsigned long int xtmp = state->x1;
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state->x1 = schrage_mult (AA1, state->x1, MM, CEIL_SQRT_MM)
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+ schrage_mult (AA2, state->x0, MM, CEIL_SQRT_MM);
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if (state->x1 >= MM)
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state->x1 -= MM;
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state->x0 = xtmp;
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return state->x1;
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}
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static double
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ran_get_double (void *vstate)
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{
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ran_state_t *state = (ran_state_t *) vstate;
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return ran_get (state) / 2147483647.0;
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}
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static void
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ran_set (void *vstate, unsigned long int s)
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{
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ran_state_t *state = (ran_state_t *) vstate;
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if ((s % MM) == 0)
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s = 1; /* default seed is 1 */
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state->x0 = s % MM;
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state->x1 = s % MM;
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return;
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}
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static const gsl_rng_type ran_type = {
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"knuthran2", /* name */
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MM - 1L, /* RAND_MAX */
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0, /* RAND_MIN */
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sizeof (ran_state_t),
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&ran_set,
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&ran_get,
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&ran_get_double
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};
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const gsl_rng_type *gsl_rng_knuthran2 = &ran_type;
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