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#include <math.h>
#include <string.h>
#include <stdio.h>
#include "../hash.h"
#include "gauss.h"
#define GAUSS_ITERS 12
static int gauss_dev(struct gauss_state *gs)
{
unsigned int r;
int vr;
if (!gs->stddev)
return 0;
r = __rand(&gs->r);
vr = gs->stddev * (r / (FRAND32_MAX + 1.0));
return vr - gs->stddev / 2;
}
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;
}
if (!gs->disable_hash)
sum = __hash_u64(sum);
return sum % gs->nranges;
}
void gauss_init(struct gauss_state *gs, unsigned long nranges, double dev,
unsigned int seed)
{
memset(gs, 0, sizeof(*gs));
init_rand_seed(&gs->r, seed, 0);
gs->nranges = nranges;
if (dev != 0.0) {
gs->stddev = ceil((double) (nranges * 100.0) / dev);
if (gs->stddev > nranges / 2)
gs->stddev = nranges / 2;
}
}
void gauss_disable_hash(struct gauss_state *gs)
{
gs->disable_hash = true;
}
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