Jens Axboe | 79c94bd | 2010-03-25 23:13:32 +0100 | [diff] [blame] | 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 | |
Jens Axboe | 1fbbf72 | 2010-03-25 23:03:18 +0100 | [diff] [blame] | 36 | #include "rand.h" |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 37 | #include "../hash.h" |
Jens Axboe | 1fbbf72 | 2010-03-25 23:03:18 +0100 | [diff] [blame] | 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 | } |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 61 | |
Jens Axboe | 7d9fb45 | 2011-01-11 22:16:49 +0100 | [diff] [blame^] | 62 | void __fill_random_buf(void *buf, unsigned int len, unsigned long seed) |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 63 | { |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 64 | long *ptr = buf; |
| 65 | |
Jens Axboe | 7d9fb45 | 2011-01-11 22:16:49 +0100 | [diff] [blame^] | 66 | while ((void *) ptr - buf < len) { |
| 67 | *ptr = seed; |
| 68 | ptr++; |
| 69 | seed *= GOLDEN_RATIO_PRIME; |
| 70 | seed >>= 3; |
| 71 | } |
| 72 | } |
| 73 | |
| 74 | unsigned long fill_random_buf(void *buf, unsigned int len) |
| 75 | { |
| 76 | unsigned long r = __rand(&__fio_rand_state); |
| 77 | |
| 78 | if (sizeof(int) != sizeof(long *)) |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 79 | r *= (unsigned long) __rand(&__fio_rand_state); |
| 80 | |
Jens Axboe | 7d9fb45 | 2011-01-11 22:16:49 +0100 | [diff] [blame^] | 81 | __fill_random_buf(buf, len, r); |
| 82 | return r; |
Jens Axboe | 637ef8d | 2010-06-21 20:39:38 +0200 | [diff] [blame] | 83 | } |