Commit | Line | Data |
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79c94bd3 JA |
1 | /* |
2 | This is a maximally equidistributed combined Tausworthe generator | |
3 | based on code from GNU Scientific Library 1.5 (30 Jun 2004) | |
4 | ||
5 | x_n = (s1_n ^ s2_n ^ s3_n) | |
6 | ||
7 | s1_{n+1} = (((s1_n & 4294967294) <<12) ^ (((s1_n <<13) ^ s1_n) >>19)) | |
8 | s2_{n+1} = (((s2_n & 4294967288) << 4) ^ (((s2_n << 2) ^ s2_n) >>25)) | |
9 | s3_{n+1} = (((s3_n & 4294967280) <<17) ^ (((s3_n << 3) ^ s3_n) >>11)) | |
10 | ||
11 | The period of this generator is about 2^88. | |
12 | ||
13 | From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe | |
14 | Generators", Mathematics of Computation, 65, 213 (1996), 203--213. | |
15 | ||
16 | This is available on the net from L'Ecuyer's home page, | |
17 | ||
18 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps | |
19 | ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps | |
20 | ||
21 | There is an erratum in the paper "Tables of Maximally | |
22 | Equidistributed Combined LFSR Generators", Mathematics of | |
23 | Computation, 68, 225 (1999), 261--269: | |
24 | http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps | |
25 | ||
26 | ... the k_j most significant bits of z_j must be non- | |
27 | zero, for each j. (Note: this restriction also applies to the | |
28 | computer code given in [4], but was mistakenly not mentioned in | |
29 | that paper.) | |
30 | ||
31 | This affects the seeding procedure by imposing the requirement | |
32 | s1 > 1, s2 > 7, s3 > 15. | |
33 | ||
34 | */ | |
35 | ||
9c42684e | 36 | #include <string.h> |
1fbbf72e | 37 | #include "rand.h" |
637ef8d9 | 38 | #include "../hash.h" |
1fbbf72e | 39 | |
1fbbf72e JA |
40 | static inline int __seed(unsigned int x, unsigned int m) |
41 | { | |
42 | return (x < m) ? x + m : x; | |
43 | } | |
44 | ||
2615cc4b JA |
45 | static void __init_rand(struct frand_state *state, unsigned int seed) |
46 | { | |
47 | int cranks = 6; | |
48 | ||
49 | #define LCG(x, seed) ((x) * 69069 ^ (seed)) | |
50 | ||
51 | state->s1 = __seed(LCG((2^31) + (2^17) + (2^7), seed), 1); | |
52 | state->s2 = __seed(LCG(state->s1, seed), 7); | |
53 | state->s3 = __seed(LCG(state->s2, seed), 15); | |
54 | ||
55 | while (cranks--) | |
56 | __rand(state); | |
57 | } | |
58 | ||
1fbbf72e JA |
59 | void init_rand(struct frand_state *state) |
60 | { | |
2615cc4b JA |
61 | __init_rand(state, 1); |
62 | } | |
63 | ||
64 | void init_rand_seed(struct frand_state *state, unsigned int seed) | |
65 | { | |
66 | __init_rand(state, seed); | |
1fbbf72e | 67 | } |
637ef8d9 | 68 | |
7d9fb455 | 69 | void __fill_random_buf(void *buf, unsigned int len, unsigned long seed) |
637ef8d9 | 70 | { |
637ef8d9 JA |
71 | long *ptr = buf; |
72 | ||
637ef8d9 | 73 | while ((void *) ptr - buf < len) { |
7d9fb455 | 74 | *ptr = seed; |
637ef8d9 | 75 | ptr++; |
7d9fb455 JA |
76 | seed *= GOLDEN_RATIO_PRIME; |
77 | seed >>= 3; | |
637ef8d9 JA |
78 | } |
79 | } | |
7d9fb455 | 80 | |
3545a109 JA |
81 | unsigned long fill_random_buf(struct frand_state *fs, void *buf, |
82 | unsigned int len) | |
7d9fb455 | 83 | { |
3545a109 | 84 | unsigned long r = __rand(fs); |
7d9fb455 JA |
85 | |
86 | if (sizeof(int) != sizeof(long *)) | |
3545a109 | 87 | r *= (unsigned long) __rand(fs); |
7d9fb455 JA |
88 | |
89 | __fill_random_buf(buf, len, r); | |
90 | return r; | |
91 | } | |
9c42684e JA |
92 | |
93 | unsigned long fill_random_buf_percentage(struct frand_state *fs, void *buf, | |
94 | unsigned int percentage, | |
95 | unsigned int segment, unsigned int len) | |
96 | { | |
9c42684e | 97 | unsigned long r = __rand(fs); |
811ac503 | 98 | unsigned int this_len; |
9c42684e | 99 | |
811ac503 JA |
100 | if (percentage == 100) { |
101 | memset(buf, 0, len); | |
102 | return 0; | |
103 | } | |
104 | ||
105 | if (segment > len) | |
106 | segment = len; | |
9c42684e JA |
107 | |
108 | if (sizeof(int) != sizeof(long *)) | |
109 | r *= (unsigned long) __rand(fs); | |
110 | ||
111 | while (len) { | |
112 | /* | |
113 | * Fill random chunk | |
114 | */ | |
115 | this_len = (segment * (100 - percentage)) / 100; | |
116 | if (this_len > len) | |
117 | this_len = len; | |
118 | ||
119 | __fill_random_buf(buf, this_len, r); | |
120 | ||
121 | len -= this_len; | |
122 | buf += this_len; | |
123 | ||
811ac503 JA |
124 | if (this_len > len) |
125 | this_len = len; | |
9c42684e | 126 | |
811ac503 | 127 | memset(buf, 0, this_len); |
98836539 JA |
128 | len -= this_len; |
129 | buf += this_len; | |
9c42684e JA |
130 | } |
131 | ||
132 | return r; | |
133 | } |