123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150 |
- /* rng/mrg.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 fifth-order multiple recursive generator. The sequence is,
- x_n = (a_1 x_{n-1} + a_5 x_{n-5}) mod m
- with a_1 = 107374182, a_2 = a_3 = a_4 = 0, a_5 = 104480 and m = 2^31-1.
- We initialize the generator with x_n = s_n MOD m for n = 1..5,
- where s_n = (69069 * s_{n-1}) mod 2^32, and s_0 = s is the
- user-supplied seed.
- NOTE: According to the paper the seeds must lie in the range [0,
- 2^31 - 2] with at least one non-zero value -- our seeding procedure
- satisfies these constraints.
- We then use 6 iterations of the generator to "warm up" the internal
- state.
- With this initialization procedure the theoretical value of
- z_{10006} is 2064828650 for s = 1. The subscript 10006 means (1)
- seed the generator with s = 1, (2) do the 6 warm-up iterations
- that are part of the seeding process, (3) then do 10000 actual
- iterations.
- The period of this generator is about 2^155.
- From: P. L'Ecuyer, F. Blouin, and R. Coutre, "A search for good
- multiple recursive random number generators", ACM Transactions on
- Modeling and Computer Simulation 3, 87-98 (1993). */
- static inline unsigned long int mrg_get (void *vstate);
- static double mrg_get_double (void *vstate);
- static void mrg_set (void *state, unsigned long int s);
- static const long int m = 2147483647;
- static const long int a1 = 107374182, q1 = 20, r1 = 7;
- static const long int a5 = 104480, q5 = 20554, r5 = 1727;
- typedef struct
- {
- long int x1, x2, x3, x4, x5;
- }
- mrg_state_t;
- static inline unsigned long int
- mrg_get (void *vstate)
- {
- mrg_state_t *state = (mrg_state_t *) vstate;
- long int p1, h1, p5, h5;
- h5 = state->x5 / q5;
- p5 = a5 * (state->x5 - h5 * q5) - h5 * r5;
- if (p5 > 0)
- p5 -= m;
- h1 = state->x1 / q1;
- p1 = a1 * (state->x1 - h1 * q1) - h1 * r1;
- if (p1 < 0)
- p1 += m;
- state->x5 = state->x4;
- state->x4 = state->x3;
- state->x3 = state->x2;
- state->x2 = state->x1;
- state->x1 = p1 + p5;
- if (state->x1 < 0)
- state->x1 += m;
- return state->x1;
- }
- static double
- mrg_get_double (void *vstate)
- {
- return mrg_get (vstate) / 2147483647.0 ;
- }
- static void
- mrg_set (void *vstate, unsigned long int s)
- {
- /* An entirely adhoc way of seeding! This does **not** come from
- L'Ecuyer et al */
- mrg_state_t *state = (mrg_state_t *) vstate;
- if (s == 0)
- s = 1; /* default seed is 1 */
- #define LCG(n) ((69069 * n) & 0xffffffffUL)
- s = LCG (s);
- state->x1 = s % m;
- s = LCG (s);
- state->x2 = s % m;
- s = LCG (s);
- state->x3 = s % m;
- s = LCG (s);
- state->x4 = s % m;
- s = LCG (s);
- state->x5 = s % m;
- /* "warm it up" with at least 5 calls to go through
- all the x values */
- mrg_get (state);
- mrg_get (state);
- mrg_get (state);
- mrg_get (state);
- mrg_get (state);
- mrg_get (state);
- return;
- }
- static const gsl_rng_type mrg_type =
- {"mrg", /* name */
- 2147483646, /* RAND_MAX */
- 0, /* RAND_MIN */
- sizeof (mrg_state_t),
- &mrg_set,
- &mrg_get,
- &mrg_get_double};
- const gsl_rng_type *gsl_rng_mrg = &mrg_type;
|