blob: e75dc2aa64409f923daeede3d28941da57b38f4e [file] [log] [blame]
#include <math.h>
#include <string.h>
#include <inttypes.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include "ieee754.h"
#include "../log.h"
#include "zipf.h"
#include "../minmax.h"
#include "../hash.h"
#define ZIPF_MAX_GEN 10000000UL
static void zipf_update(struct zipf_state *zs)
{
unsigned long to_gen;
unsigned int i;
/*
* It can become very costly to generate long sequences. Just cap it at
* 10M max, that should be doable in 1-2s on even slow machines.
* Precision will take a slight hit, but nothing major.
*/
to_gen = min(zs->nranges, ZIPF_MAX_GEN);
for (i = 0; i < to_gen; i++)
zs->zetan += pow(1.0 / (double) (i + 1), zs->theta);
}
static void shared_rand_init(struct zipf_state *zs, unsigned long nranges,
unsigned int seed)
{
memset(zs, 0, sizeof(*zs));
zs->nranges = nranges;
init_rand_seed(&zs->rand, seed);
zs->rand_off = __rand(&zs->rand);
}
void zipf_init(struct zipf_state *zs, unsigned long nranges, double theta,
unsigned int seed)
{
shared_rand_init(zs, nranges, seed);
zs->theta = theta;
zs->zeta2 = pow(1.0, zs->theta) + pow(0.5, zs->theta);
zipf_update(zs);
}
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) FRAND_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));
return (__hash_u64(val - 1) + zs->rand_off) % zs->nranges;
}
void pareto_init(struct zipf_state *zs, unsigned long nranges, double h,
unsigned int seed)
{
shared_rand_init(zs, nranges, seed);
zs->pareto_pow = log(h) / log(1.0 - h);
}
unsigned long long pareto_next(struct zipf_state *zs)
{
double rand = (double) __rand(&zs->rand) / (double) FRAND_MAX;
unsigned long long n = zs->nranges - 1;
return (__hash_u64(n * pow(rand, zs->pareto_pow)) + zs->rand_off) % zs->nranges;
}