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79c94bd3
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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
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
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40static inline int __seed(unsigned int x, unsigned int m)
41{
42 return (x < m) ? x + m : x;
43}
44
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45static 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
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59void init_rand(struct frand_state *state)
60{
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61 __init_rand(state, 1);
62}
63
64void init_rand_seed(struct frand_state *state, unsigned int seed)
65{
66 __init_rand(state, seed);
1fbbf72e 67}
637ef8d9 68
7d9fb455 69void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)
637ef8d9 70{
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71 long *ptr = buf;
72
637ef8d9 73 while ((void *) ptr - buf < len) {
7d9fb455 74 *ptr = seed;
637ef8d9 75 ptr++;
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76 seed *= GOLDEN_RATIO_PRIME;
77 seed >>= 3;
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78 }
79}
7d9fb455 80
3545a109
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81unsigned long fill_random_buf(struct frand_state *fs, void *buf,
82 unsigned int len)
7d9fb455 83{
3545a109 84 unsigned long r = __rand(fs);
7d9fb455
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85
86 if (sizeof(int) != sizeof(long *))
3545a109 87 r *= (unsigned long) __rand(fs);
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88
89 __fill_random_buf(buf, len, r);
90 return r;
91}
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92
93unsigned 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
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100 if (percentage == 100) {
101 memset(buf, 0, len);
102 return 0;
103 }
104
105 if (segment > len)
106 segment = len;
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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
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124 if (this_len > len)
125 this_len = len;
9c42684e 126
811ac503 127 memset(buf, 0, this_len);
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128 }
129
130 return r;
131}