9 static int gauss_dev(struct gauss_state *gs)
18 vr = gs->stddev * (r / (FRAND32_MAX + 1.0));
20 return vr - gs->stddev / 2;
23 unsigned long long gauss_next(struct gauss_state *gs)
25 unsigned long long sum = 0;
28 for (i = 0; i < GAUSS_ITERS; i++)
29 sum += __rand(&gs->r) % (gs->nranges + 1);
31 sum = (sum + GAUSS_ITERS - 1) / GAUSS_ITERS;
34 int dev = gauss_dev(gs);
36 while (dev + sum >= gs->nranges)
41 if (!gs->disable_hash)
42 sum = __hash_u64(sum);
44 return sum % gs->nranges;
47 void gauss_init(struct gauss_state *gs, unsigned long nranges, double dev,
50 memset(gs, 0, sizeof(*gs));
51 init_rand_seed(&gs->r, seed, 0);
52 gs->nranges = nranges;
55 gs->stddev = ceil((double) (nranges * 100.0) / dev);
56 if (gs->stddev > nranges / 2)
57 gs->stddev = nranges / 2;
61 void gauss_disable_hash(struct gauss_state *gs)
63 gs->disable_hash = true;