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[svn r136] MAJOR UNSTABLE UPDATE!!! Initial commit after moving to Tango instead of Phobos. Lots of bugfixes... This build is not suitable for most things.
author lindquist
date Fri, 11 Jan 2008 17:57:40 +0100
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131:5825d48b27d1 132:1700239cab2e
1 /*******************************************************************************
2
3 copyright: Copyright (c) 2004. All rights reserved
4
5 license: BSD style: $(LICENSE)
6
7 version: Initial release: April 2004
8
9 author: Various
10
11 *******************************************************************************/
12
13 module tango.math.Random;
14
15
16 version (Win32)
17 private extern(Windows) int QueryPerformanceCounter (ulong *);
18
19 version (Posix)
20 {
21 private import tango.stdc.posix.sys.time;
22 }
23
24
25 /******************************************************************************
26
27 KISS (via George Marsaglia & Paul Hsieh)
28
29 the idea is to use simple, fast, individually promising
30 generators to get a composite that will be fast, easy to code
31 have a very long period and pass all the tests put to it.
32 The three components of KISS are
33
34 x(n)=a*x(n-1)+1 mod 2^32
35 y(n)=y(n-1)(I+L^13)(I+R^17)(I+L^5),
36 z(n)=2*z(n-1)+z(n-2) +carry mod 2^32
37
38 The y's are a shift register sequence on 32bit binary vectors
39 period 2^32-1; The z's are a simple multiply-with-carry sequence
40 with period 2^63+2^32-1.
41
42 The period of KISS is thus 2^32*(2^32-1)*(2^63+2^32-1) > 2^127
43
44 ******************************************************************************/
45
46 class Random
47 {
48 /**********************************************************************
49
50 Shared instance:
51 ---
52 auto random = Random.shared.next;
53 ---
54
55 **********************************************************************/
56 public static Random shared;
57
58 private uint kiss_k;
59 private uint kiss_m;
60 private uint kiss_x = 1;
61 private uint kiss_y = 2;
62 private uint kiss_z = 4;
63 private uint kiss_w = 8;
64 private uint kiss_carry = 0;
65
66 /**********************************************************************
67
68 Create a static and shared instance:
69 ---
70 auto random = Random.shared.next;
71 ---
72
73 **********************************************************************/
74
75 static this ()
76 {
77 shared = new Random;
78 }
79
80 /**********************************************************************
81
82 Creates and seeds a new generator with the current time
83
84 **********************************************************************/
85
86 this ()
87 {
88 this.seed;
89 }
90
91 /**********************************************************************
92
93 Seed the generator with current time
94
95 **********************************************************************/
96
97 final Random seed ()
98 {
99 ulong s;
100
101 version (Posix)
102 {
103 timeval tv;
104
105 gettimeofday (&tv, null);
106 s = tv.tv_usec;
107 }
108 version (Win32)
109 QueryPerformanceCounter (&s);
110
111 return seed (cast(uint) s);
112 }
113
114 /**********************************************************************
115
116 Seed the generator with a provided value
117
118 **********************************************************************/
119
120 final Random seed (uint seed)
121 {
122 kiss_x = seed | 1;
123 kiss_y = seed | 2;
124 kiss_z = seed | 4;
125 kiss_w = seed | 8;
126 kiss_carry = 0;
127 return this;
128 }
129
130 /**********************************************************************
131
132 Returns X such that 0 <= X <= uint.max
133
134 **********************************************************************/
135
136 final uint next ()
137 {
138 kiss_x = kiss_x * 69069 + 1;
139 kiss_y ^= kiss_y << 13;
140 kiss_y ^= kiss_y >> 17;
141 kiss_y ^= kiss_y << 5;
142 kiss_k = (kiss_z >> 2) + (kiss_w >> 3) + (kiss_carry >> 2);
143 kiss_m = kiss_w + kiss_w + kiss_z + kiss_carry;
144 kiss_z = kiss_w;
145 kiss_w = kiss_m;
146 kiss_carry = kiss_k >> 30;
147 return kiss_x + kiss_y + kiss_w;
148 }
149
150 /**********************************************************************
151
152 Returns X such that 0 <= X < max
153
154 Note that max is exclusive, making it compatible with
155 array indexing
156
157 **********************************************************************/
158
159 final uint next (uint max)
160 {
161 return next() % max;
162 }
163
164 /**********************************************************************
165
166 Returns X such that min <= X < max
167
168 Note that max is exclusive, making it compatible with
169 array indexing
170
171 **********************************************************************/
172
173 final uint next (uint min, uint max)
174 {
175 return next(max-min) + min;
176 }
177 }
178