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 | ||
1fbbf72e | 36 | #include "rand.h" |
637ef8d9 | 37 | #include "../hash.h" |
1fbbf72e JA |
38 | |
39 | struct frand_state __fio_rand_state; | |
40 | ||
41 | static inline int __seed(unsigned int x, unsigned int m) | |
42 | { | |
43 | return (x < m) ? x + m : x; | |
44 | } | |
45 | ||
46 | void init_rand(struct frand_state *state) | |
47 | { | |
48 | #define LCG(x) ((x) * 69069) /* super-duper LCG */ | |
49 | ||
50 | state->s1 = __seed(LCG((2^31) + (2^17) + (2^7)), 1); | |
51 | state->s2 = __seed(LCG(state->s1), 7); | |
52 | state->s3 = __seed(LCG(state->s2), 15); | |
53 | ||
54 | __rand(state); | |
55 | __rand(state); | |
56 | __rand(state); | |
57 | __rand(state); | |
58 | __rand(state); | |
59 | __rand(state); | |
60 | } | |
637ef8d9 JA |
61 | |
62 | void fill_random_buf(void *buf, unsigned int len) | |
63 | { | |
64 | unsigned long r = __rand(&__fio_rand_state); | |
65 | long *ptr = buf; | |
66 | ||
67 | if (sizeof(int) != sizeof(*ptr)) | |
68 | r *= (unsigned long) __rand(&__fio_rand_state); | |
69 | ||
70 | while ((void *) ptr - buf < len) { | |
71 | *ptr = r; | |
72 | ptr++; | |
73 | r *= GOLDEN_RATIO_PRIME; | |
74 | r >>= 3; | |
75 | } | |
76 | } |