8 static int gauss_dev(struct gauss_state *gs)
17 vr = gs->stddev * (r / (FRAND32_MAX + 1.0));
19 return vr - gs->stddev / 2;
22 unsigned long long gauss_next(struct gauss_state *gs)
24 unsigned long long sum = 0;
27 for (i = 0; i < GAUSS_ITERS; i++)
28 sum += __rand(&gs->r) % (gs->nranges + 1);
30 sum = (sum + GAUSS_ITERS - 1) / GAUSS_ITERS;
33 int dev = gauss_dev(gs);
35 while (dev + sum >= gs->nranges)
40 if (!gs->disable_hash)
41 sum = __hash_u64(sum);
43 return sum % gs->nranges;
46 void gauss_init(struct gauss_state *gs, unsigned long nranges, double dev,
49 memset(gs, 0, sizeof(*gs));
50 init_rand_seed(&gs->r, seed, 0);
51 gs->nranges = nranges;
54 gs->stddev = ceil((double) (nranges * 100.0) / dev);
55 if (gs->stddev > nranges / 2)
56 gs->stddev = nranges / 2;
60 void gauss_disable_hash(struct gauss_state *gs)
62 gs->disable_hash = true;