| /* rng/ran0.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_errno.h> |
| #include <gsl/gsl_rng.h> |
| |
| /* This is an implementation of the algorithm used in Numerical |
| Recipe's ran0 generator. It is the same as MINSTD with an XOR mask |
| of 123459876 on the seed. |
| |
| The period of this generator is 2^31. |
| |
| Note, if you choose a seed of 123459876 it would give a degenerate |
| series 0,0,0,0, ... I've made that into an error. */ |
| |
| static inline unsigned long int ran0_get (void *vstate); |
| static double ran0_get_double (void *vstate); |
| static void ran0_set (void *state, unsigned long int s); |
| |
| static const long int m = 2147483647, a = 16807, q = 127773, r = 2836; |
| static const unsigned long int mask = 123459876; |
| |
| typedef struct |
| { |
| unsigned long int x; |
| } |
| ran0_state_t; |
| |
| static inline unsigned long int |
| ran0_get (void *vstate) |
| { |
| ran0_state_t *state = (ran0_state_t *) vstate; |
| |
| const unsigned long int x = state->x; |
| |
| const long int h = x / q; |
| const long int t = a * (x - h * q) - h * r; |
| |
| if (t < 0) |
| { |
| state->x = t + m; |
| } |
| else |
| { |
| state->x = t; |
| } |
| |
| return state->x; |
| } |
| |
| static double |
| ran0_get_double (void *vstate) |
| { |
| return ran0_get (vstate) / 2147483647.0 ; |
| } |
| |
| static void |
| ran0_set (void *vstate, unsigned long int s) |
| { |
| ran0_state_t *state = (ran0_state_t *) vstate; |
| |
| if (s == mask) |
| { |
| GSL_ERROR_VOID ("ran0 should not use seed == mask", |
| GSL_EINVAL); |
| } |
| |
| state->x = s ^ mask; |
| |
| return; |
| } |
| |
| static const gsl_rng_type ran0_type = |
| {"ran0", /* name */ |
| 2147483646, /* RAND_MAX */ |
| 1, /* RAND_MIN */ |
| sizeof (ran0_state_t), |
| &ran0_set, |
| &ran0_get, |
| &ran0_get_double}; |
| |
| const gsl_rng_type *gsl_rng_ran0 = &ran0_type; |