1 /* rng/vax.c
2 *
3 * Copyright (C) 1996, 1997, 1998, 1999, 2000, 2007 James Theiler, Brian Gough
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 3 of the License, or (at
8 * your option) any later version.
9 *
10 * This program is distributed in the hope that it will be useful, but
11 * WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * General Public License for more details.
14 *
15 * You should have received a copy of the GNU General Public License
16 * along with this program; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
18 */
19
20 #include "gsl__config.h"
21 #include <stdlib.h>
22 #include "gsl_rng.h"
23
24 /* This is the old vax generator MTH$RANDOM. The sequence is,
25
26 x_{n+1} = (a x_n + c) mod m
27
28 with a = 69069, c = 1 and m = 2^32. The seed specifies the initial
29 value, x_1.
30
31 The theoretical value of x_{10001} is 3051034865.
32
33 The period of this generator is 2^32. */
34
35 static inline unsigned long int vax_get (void *vstate);
36 static double vax_get_double (void *vstate);
37 static void vax_set (void *state, unsigned long int s);
38
39 typedef struct
40 {
41 unsigned long int x;
42 }
43 vax_state_t;
44
45 static inline unsigned long int
vax_get(void * vstate)46 vax_get (void *vstate)
47 {
48 vax_state_t *state = (vax_state_t *) vstate;
49
50 state->x = (69069 * state->x + 1) & 0xffffffffUL;
51
52 return state->x;
53 }
54
55 static double
vax_get_double(void * vstate)56 vax_get_double (void *vstate)
57 {
58 return vax_get (vstate) / 4294967296.0 ;
59 }
60
61 static void
vax_set(void * vstate,unsigned long int s)62 vax_set (void *vstate, unsigned long int s)
63 {
64 vax_state_t *state = (vax_state_t *) vstate;
65
66 /* default seed is 0. The constant term c stops the series from
67 collapsing to 0,0,0,0,0,... */
68
69 state->x = s;
70
71 return;
72 }
73
74 static const gsl_rng_type vax_type =
75 {"vax", /* name */
76 0xffffffffUL, /* RAND_MAX */
77 0, /* RAND_MIN */
78 sizeof (vax_state_t),
79 &vax_set,
80 &vax_get,
81 &vax_get_double};
82
83 const gsl_rng_type *gsl_rng_vax = &vax_type;
84