| /* rng/rand.c |
| * |
| * Copyright (C) 1996, 1997, 1998, 1999, 2000 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 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. |
| */ |
| |
| #include <config.h> |
| #include <stdlib.h> |
| #include <gsl/gsl_rng.h> |
| |
| /* This is the old BSD rand() generator. The sequence is |
| |
| x_{n+1} = (a x_n + c) mod m |
| |
| with a = 1103515245, c = 12345 and m = 2^31 = 2147483648. The seed |
| specifies the initial value, x_1. |
| |
| The theoretical value of x_{10001} is 1910041713. |
| |
| The period of this generator is 2^31. |
| |
| The rand() generator is not very good -- the low bits of successive |
| numbers are correlated. */ |
| |
| static inline unsigned long int rand_get (void *vstate); |
| static double rand_get_double (void *vstate); |
| static void rand_set (void *state, unsigned long int s); |
| |
| typedef struct |
| { |
| unsigned long int x; |
| } |
| rand_state_t; |
| |
| static inline unsigned long int |
| rand_get (void *vstate) |
| { |
| rand_state_t *state = (rand_state_t *) vstate; |
| |
| /* The following line relies on unsigned 32-bit arithmetic */ |
| |
| state->x = (1103515245 * state->x + 12345) & 0x7fffffffUL; |
| |
| return state->x; |
| } |
| |
| static double |
| rand_get_double (void *vstate) |
| { |
| return rand_get (vstate) / 2147483648.0 ; |
| } |
| |
| static void |
| rand_set (void *vstate, unsigned long int s) |
| { |
| rand_state_t *state = (rand_state_t *) vstate; |
| |
| state->x = s; |
| |
| return; |
| } |
| |
| static const gsl_rng_type rand_type = |
| {"rand", /* name */ |
| 0x7fffffffUL, /* RAND_MAX */ |
| 0, /* RAND_MIN */ |
| sizeof (rand_state_t), |
| &rand_set, |
| &rand_get, |
| &rand_get_double}; |
| |
| const gsl_rng_type *gsl_rng_rand = &rand_type; |