2 This is a maximally equidistributed combined Tausworthe generator
3 based on code from GNU Scientific Library 1.5 (30 Jun 2004)
5 x_n = (s1_n ^ s2_n ^ s3_n)
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))
11 The period of this generator is about 2^88.
13 From: P. L'Ecuyer, "Maximally Equidistributed Combined Tausworthe
14 Generators", Mathematics of Computation, 65, 213 (1996), 203--213.
16 This is available on the net from L'Ecuyer's home page,
18 http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps
19 ftp://ftp.iro.umontreal.ca/pub/simulation/lecuyer/papers/tausme.ps
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
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
31 This affects the seeding procedure by imposing the requirement
32 s1 > 1, s2 > 7, s3 > 15.
41 static inline int __seed(unsigned int x, unsigned int m)
43 return (x < m) ? x + m : x;
46 static void __init_rand(struct frand_state *state, unsigned int seed)
50 #define LCG(x, seed) ((x) * 69069 ^ (seed))
52 state->s1 = __seed(LCG((2^31) + (2^17) + (2^7), seed), 1);
53 state->s2 = __seed(LCG(state->s1, seed), 7);
54 state->s3 = __seed(LCG(state->s2, seed), 15);
60 void init_rand(struct frand_state *state)
62 __init_rand(state, 1);
65 void init_rand_seed(struct frand_state *state, unsigned int seed)
67 __init_rand(state, seed);
70 void __fill_random_buf(void *buf, unsigned int len, unsigned long seed)
77 if (len >= sizeof(int64_t)) {
78 *((int64_t *) ptr) = seed;
79 this_len = sizeof(int64_t);
80 } else if (len >= sizeof(int32_t)) {
81 *((int32_t *) ptr) = seed;
82 this_len = sizeof(int32_t);
83 } else if (len >= sizeof(int16_t)) {
84 *((int16_t *) ptr) = seed;
85 this_len = sizeof(int16_t);
87 *((int8_t *) ptr) = seed;
88 this_len = sizeof(int8_t);
92 seed *= GOLDEN_RATIO_PRIME;
97 unsigned long fill_random_buf(struct frand_state *fs, void *buf,
100 unsigned long r = __rand(fs);
102 if (sizeof(int) != sizeof(long *))
103 r *= (unsigned long) __rand(fs);
105 __fill_random_buf(buf, len, r);
109 void fill_pattern(void *p, unsigned int len, char *pattern,
110 unsigned int pattern_bytes)
112 switch (pattern_bytes) {
117 memset(p, pattern[0], len);
120 unsigned int i = 0, size = 0;
121 unsigned char *b = p;
124 size = pattern_bytes;
125 if (size > (len - i))
127 memcpy(b+i, pattern, size);
135 void __fill_random_buf_percentage(unsigned long seed, void *buf,
136 unsigned int percentage,
137 unsigned int segment, unsigned int len,
138 char *pattern, unsigned int pbytes)
140 unsigned int this_len;
142 if (percentage == 100) {
144 fill_pattern(buf, len, pattern, pbytes);
157 this_len = (segment * (100 - percentage)) / 100;
161 __fill_random_buf(buf, this_len, seed);
170 else if (len - this_len <= sizeof(long))
174 fill_pattern(buf, this_len, pattern, pbytes);
176 memset(buf, 0, this_len);
183 unsigned long fill_random_buf_percentage(struct frand_state *fs, void *buf,
184 unsigned int percentage,
185 unsigned int segment, unsigned int len,
186 char *pattern, unsigned int pbytes)
188 unsigned long r = __rand(fs);
190 if (sizeof(int) != sizeof(long *))
191 r *= (unsigned long) __rand(fs);
193 __fill_random_buf_percentage(r, buf, percentage, segment, len,