unsigned long long zipf_next(struct zipf_state *zs)
{
double alpha, eta, rand_uni, rand_z;
unsigned long long n = zs->nranges;
unsigned long long val;
alpha = 1.0 / (1.0 - zs->theta);
eta = (1.0 - pow(2.0 / n, 1.0 - zs->theta)) / (1.0 - zs->zeta2 / zs->zetan);
rand_uni = (double) __rand(&zs->rand) / (double) FRAND32_MAX;
rand_z = rand_uni * zs->zetan;
if (rand_z < 1.0)
val = 1;
else if (rand_z < (1.0 + pow(0.5, zs->theta)))
val = 2;
else
val = 1 + (unsigned long long)(n * pow(eta*rand_uni - eta + 1.0, alpha));
val--;
if (!zs->disable_hash)
val = __hash_u64(val);
return (val + zs->rand_off) % zs->nranges;
}
unsigned long long pareto_next(struct zipf_state *zs)
{
double rand = (double) __rand(&zs->rand) / (double) FRAND32_MAX;
unsigned long long n;
n = (zs->nranges - 1) * pow(rand, zs->pareto_pow);
if (!zs->disable_hash)
n = __hash_u64(n);
return (n + zs->rand_off) % zs->nranges;
}
unsigned long long gauss_next(struct gauss_state *gs)
{
unsigned long long sum = 0;
int i;
for (i = 0; i < GAUSS_ITERS; i++)
sum += __rand(&gs->r) % (gs->nranges + 1);
sum = (sum + GAUSS_ITERS - 1) / GAUSS_ITERS;
if (gs->stddev) {
int dev = gauss_dev(gs);
while (dev + sum >= gs->nranges)
dev /= 2;
sum += dev;
}
return __hash_u64(sum) % gs->nranges;
}
