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- /* rng/ranlux.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 a lagged fibonacci generator with skipping developed by Luescher.
- The sequence is a series of 24-bit integers, x_n,
- x_n = d_n + b_n
- where d_n = x_{n-10} - x_{n-24} - c_{n-1}, b_n = 0 if d_n >= 0 and
- b_n = 2^24 if d_n < 0, c_n = 0 if d_n >= 0 and c_n = 1 if d_n < 0,
- where after 24 samples a group of p integers are "skipped", to
- reduce correlations. By default p = 199, but can be increased to
- 365.
- The period of the generator is around 10^171.
- From: M. Luescher, "A portable high-quality random number generator
- for lattice field theory calculations", Computer Physics
- Communications, 79 (1994) 100-110.
- Available on the net as hep-lat/9309020 at http://xxx.lanl.gov/
- See also,
- F. James, "RANLUX: A Fortran implementation of the high-quality
- pseudo-random number generator of Luscher", Computer Physics
- Communications, 79 (1994) 111-114
- Kenneth G. Hamilton, F. James, "Acceleration of RANLUX", Computer
- Physics Communications, 101 (1997) 241-248
- Kenneth G. Hamilton, "Assembler RANLUX for PCs", Computer Physics
- Communications, 101 (1997) 249-253 */
- static inline unsigned long int ranlux_get (void *vstate);
- static double ranlux_get_double (void *vstate);
- static void ranlux_set_lux (void *state, unsigned long int s, unsigned int luxury);
- static void ranlux_set (void *state, unsigned long int s);
- static void ranlux389_set (void *state, unsigned long int s);
- static const unsigned long int mask_lo = 0x00ffffffUL; /* 2^24 - 1 */
- static const unsigned long int mask_hi = ~0x00ffffffUL;
- static const unsigned long int two24 = 16777216; /* 2^24 */
- typedef struct
- {
- unsigned int i;
- unsigned int j;
- unsigned int n;
- unsigned int skip;
- unsigned int carry;
- unsigned long int u[24];
- }
- ranlux_state_t;
- static inline unsigned long int increment_state (ranlux_state_t * state);
- static inline unsigned long int
- increment_state (ranlux_state_t * state)
- {
- unsigned int i = state->i;
- unsigned int j = state->j;
- long int delta = state->u[j] - state->u[i] - state->carry;
- if (delta & mask_hi)
- {
- state->carry = 1;
- delta &= mask_lo;
- }
- else
- {
- state->carry = 0;
- }
- state->u[i] = delta;
- if (i == 0)
- {
- i = 23;
- }
- else
- {
- i--;
- }
- state->i = i;
- if (j == 0)
- {
- j = 23;
- }
- else
- {
- j--;
- }
- state->j = j;
- return delta;
- }
- static inline unsigned long int
- ranlux_get (void *vstate)
- {
- ranlux_state_t *state = (ranlux_state_t *) vstate;
- const unsigned int skip = state->skip;
- unsigned long int r = increment_state (state);
- state->n++;
- if (state->n == 24)
- {
- unsigned int i;
- state->n = 0;
- for (i = 0; i < skip; i++)
- increment_state (state);
- }
- return r;
- }
- static double
- ranlux_get_double (void *vstate)
- {
- return ranlux_get (vstate) / 16777216.0;
- }
- static void
- ranlux_set_lux (void *vstate, unsigned long int s, unsigned int luxury)
- {
- ranlux_state_t *state = (ranlux_state_t *) vstate;
- int i;
- long int seed;
- if (s == 0)
- s = 314159265; /* default seed is 314159265 */
- seed = s;
- /* This is the initialization algorithm of F. James, widely in use
- for RANLUX. */
- for (i = 0; i < 24; i++)
- {
- unsigned long int k = seed / 53668;
- seed = 40014 * (seed - k * 53668) - k * 12211;
- if (seed < 0)
- {
- seed += 2147483563;
- }
- state->u[i] = seed % two24;
- }
- state->i = 23;
- state->j = 9;
- state->n = 0;
- state->skip = luxury - 24;
- if (state->u[23] & mask_hi)
- {
- state->carry = 1;
- }
- else
- {
- state->carry = 0;
- }
- }
- static void
- ranlux_set (void *vstate, unsigned long int s)
- {
- ranlux_set_lux (vstate, s, 223);
- }
- static void
- ranlux389_set (void *vstate, unsigned long int s)
- {
- ranlux_set_lux (vstate, s, 389);
- }
- static const gsl_rng_type ranlux_type =
- {"ranlux", /* name */
- 0x00ffffffUL, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (ranlux_state_t),
- &ranlux_set,
- &ranlux_get,
- &ranlux_get_double};
- static const gsl_rng_type ranlux389_type =
- {"ranlux389", /* name */
- 0x00ffffffUL, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (ranlux_state_t),
- &ranlux389_set,
- &ranlux_get,
- &ranlux_get_double};
- const gsl_rng_type *gsl_rng_ranlux = &ranlux_type;
- const gsl_rng_type *gsl_rng_ranlux389 = &ranlux389_type;
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