| /* rng/ran3.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 an implementation of the algorithm used in Knuths's |
| subtractive generator, with the Numerical Recipe's ran3 paramters. |
| It is a subtractive lagged fibonnaci generator. */ |
| |
| static inline unsigned long int ran3_get (void *vstate); |
| static double ran3_get_double (void *vstate); |
| static void ran3_set (void *state, unsigned long int s); |
| |
| #define M_BIG 1000000000 |
| #define M_SEED 161803398 |
| |
| typedef struct |
| { |
| unsigned int x; |
| unsigned int y; |
| unsigned long int buffer[56]; |
| } |
| ran3_state_t; |
| |
| static inline unsigned long int |
| ran3_get (void *vstate) |
| { |
| ran3_state_t *state = (ran3_state_t *) vstate; |
| long int j; |
| |
| state->x++; |
| |
| if (state->x == 56) |
| state->x = 1; |
| |
| state->y++; |
| |
| if (state->y == 56) |
| state->y = 1; |
| |
| j = state->buffer[state->x] - state->buffer[state->y]; |
| |
| if (j < 0) |
| j += M_BIG; |
| |
| state->buffer[state->x] = j; |
| |
| return j; |
| } |
| |
| static double |
| ran3_get_double (void *vstate) |
| { |
| return ran3_get (vstate) / (double) M_BIG ; |
| } |
| |
| static void |
| ran3_set (void *vstate, unsigned long int s) |
| { |
| ran3_state_t *state = (ran3_state_t *) vstate; |
| int i, i1; |
| long int j, k; |
| |
| if (s == 0) |
| s = 1; /* default seed is 1 */ |
| |
| j = (M_SEED - s) % M_BIG; |
| |
| /* the zeroth element is never used, but we initialize it for |
| consistency between states */ |
| |
| state->buffer[0] = 0; |
| |
| state->buffer[55] = j; |
| |
| k = 1; |
| for (i = 1; i < 55; i++) |
| { |
| int n = (21 * i) % 55; |
| state->buffer[n] = k; |
| k = j - k; |
| if (k < 0) |
| k += M_BIG; |
| j = state->buffer[n]; |
| |
| } |
| |
| for (i1 = 0; i1 < 4; i1++) |
| { |
| for (i = 1; i < 56; i++) |
| { |
| long int t = state->buffer[i] - state->buffer[1 + (i + 30) % 55]; |
| if (t < 0) |
| t += M_BIG; |
| state->buffer[i] = t; |
| } |
| } |
| |
| state->x = 0; |
| state->y = 31; |
| |
| return; |
| } |
| |
| static const gsl_rng_type ran3_type = |
| {"ran3", /* name */ |
| M_BIG, /* RAND_MAX */ |
| 0, /* RAND_MIN */ |
| sizeof (ran3_state_t), |
| &ran3_set, |
| &ran3_get, |
| &ran3_get_double}; |
| |
| const gsl_rng_type *gsl_rng_ran3 = &ran3_type; |