102 lines
2.3 KiB
C
102 lines
2.3 KiB
C
#include <math.h>
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#include <string.h>
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#include <inttypes.h>
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#include <stdio.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <fcntl.h>
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#include "ieee754.h"
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#include "zipf.h"
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#include "../minmax.h"
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#include "../hash.h"
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#define ZIPF_MAX_GEN 10000000UL
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static void zipf_update(struct zipf_state *zs)
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{
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unsigned long to_gen;
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unsigned int i;
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/*
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* It can become very costly to generate long sequences. Just cap it at
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* 10M max, that should be doable in 1-2s on even slow machines.
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* Precision will take a slight hit, but nothing major.
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*/
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to_gen = min(zs->nranges, (uint64_t) ZIPF_MAX_GEN);
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for (i = 0; i < to_gen; i++)
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zs->zetan += pow(1.0 / (double) (i + 1), zs->theta);
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}
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static void shared_rand_init(struct zipf_state *zs, unsigned long nranges,
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unsigned int seed)
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{
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memset(zs, 0, sizeof(*zs));
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zs->nranges = nranges;
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init_rand_seed(&zs->rand, seed, 0);
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zs->rand_off = __rand(&zs->rand);
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}
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void zipf_init(struct zipf_state *zs, unsigned long nranges, double theta,
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unsigned int seed)
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{
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shared_rand_init(zs, nranges, seed);
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zs->theta = theta;
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zs->zeta2 = pow(1.0, zs->theta) + pow(0.5, zs->theta);
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zipf_update(zs);
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}
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unsigned long long zipf_next(struct zipf_state *zs)
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{
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double alpha, eta, rand_uni, rand_z;
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unsigned long long n = zs->nranges;
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unsigned long long val;
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alpha = 1.0 / (1.0 - zs->theta);
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eta = (1.0 - pow(2.0 / n, 1.0 - zs->theta)) / (1.0 - zs->zeta2 / zs->zetan);
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rand_uni = (double) __rand(&zs->rand) / (double) FRAND32_MAX;
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rand_z = rand_uni * zs->zetan;
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if (rand_z < 1.0)
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val = 1;
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else if (rand_z < (1.0 + pow(0.5, zs->theta)))
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val = 2;
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else
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val = 1 + (unsigned long long)(n * pow(eta*rand_uni - eta + 1.0, alpha));
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val--;
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if (!zs->disable_hash)
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val = __hash_u64(val);
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return (val + zs->rand_off) % zs->nranges;
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}
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void pareto_init(struct zipf_state *zs, unsigned long nranges, double h,
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unsigned int seed)
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{
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shared_rand_init(zs, nranges, seed);
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zs->pareto_pow = log(h) / log(1.0 - h);
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}
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unsigned long long pareto_next(struct zipf_state *zs)
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{
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double rand = (double) __rand(&zs->rand) / (double) FRAND32_MAX;
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unsigned long long n;
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n = (zs->nranges - 1) * pow(rand, zs->pareto_pow);
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if (!zs->disable_hash)
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n = __hash_u64(n);
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return (n + zs->rand_off) % zs->nranges;
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}
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void zipf_disable_hash(struct zipf_state *zs)
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{
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zs->disable_hash = true;
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}
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