projects / fio.git / blame
| Commit | Line | Data |
|---|---|---|
| 56d9fa4b JA |
1 | #include <math.h> |
| 2 | #include <string.h> | |
| 56d9fa4b JA |
3 | #include "../hash.h" |
| 4 | #include "gauss.h" | |
| 5 | ||
| 6 | #define GAUSS_ITERS 12 | |
| 7 | ||
| 8 | static int gauss_dev(struct gauss_state *gs) | |
| 9 | { | |
| 10 | unsigned int r; | |
| 11 | int vr; | |
| 12 | ||
| 13 | if (!gs->stddev) | |
| 14 | return 0; | |
| 15 | ||
| 16 | r = __rand(&gs->r); | |
| c3546b53 | 17 | vr = gs->stddev * (r / (FRAND32_MAX + 1.0)); |
| 56d9fa4b JA |
18 | |
| 19 | return vr - gs->stddev / 2; | |
| 20 | } | |
| 21 | ||
| 22 | unsigned long long gauss_next(struct gauss_state *gs) | |
| 23 | { | |
| 24 | unsigned long long sum = 0; | |
| 25 | int i; | |
| 26 | ||
| 27 | for (i = 0; i < GAUSS_ITERS; i++) | |
| 28 | sum += __rand(&gs->r) % (gs->nranges + 1); | |
| 29 | ||
| 30 | sum = (sum + GAUSS_ITERS - 1) / GAUSS_ITERS; | |
| 31 | ||
| 32 | if (gs->stddev) { | |
| 33 | int dev = gauss_dev(gs); | |
| 34 | ||
| 35 | while (dev + sum >= gs->nranges) | |
| 36 | dev /= 2; | |
| 37 | sum += dev; | |
| 38 | } | |
| 39 | ||
| 8348daf9 | 40 | if (!gs->disable_hash) |
| 8c5e96a4 | 41 | sum = __hash_u64(sum); |
| 8348daf9 JA |
42 | |
| 43 | return sum % gs->nranges; | |
| 56d9fa4b JA |
44 | } |
| 45 | ||
| f88cd222 | 46 | void gauss_init(struct gauss_state *gs, unsigned long nranges, double dev, |
| 56d9fa4b JA |
47 | unsigned int seed) |
| 48 | { | |
| 49 | memset(gs, 0, sizeof(*gs)); | |
| c3546b53 | 50 | init_rand_seed(&gs->r, seed, 0); |
| 56d9fa4b | 51 | gs->nranges = nranges; |
| f88cd222 JA |
52 | |
| 53 | if (dev != 0.0) { | |
| 54 | gs->stddev = ceil((double) (nranges * 100.0) / dev); | |
| 3cdb8cf3 JA |
55 | if (gs->stddev > nranges / 2) |
| 56 | gs->stddev = nranges / 2; | |
| 57 | } | |
| 56d9fa4b | 58 | } |
| 8348daf9 JA |
59 | |
| 60 | void gauss_disable_hash(struct gauss_state *gs) | |
| 61 | { | |
| 62 | gs->disable_hash = true; | |
| 63 | } |