https://github.com/ntamas/plfit
test_sampling.c
/* test_sampling.c
*
* Copyright (C) 2012 Tamas Nepusz
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
#include <math.h>
#include "plfit_sampling.h"
#include "test_common.h"
#define NUM_SAMPLES 1000000
#define NUM_ITEMS 26
int test_sampling(void) {
plfit_walker_alias_sampler_t sampler;
double probs[NUM_ITEMS];
double prob_sum = 0.0;
long int* data;
long int hist[NUM_ITEMS];
long int i, j, max_hist;
plfit_mt_rng_t rng;
data = calloc(NUM_SAMPLES, sizeof(long int));
if (data == 0) {
return 3;
}
plfit_mt_init(&rng);
/* Create the sampler, sample, destroy */
for (i = 0; i < NUM_ITEMS; i++) {
probs[i] = i;
prob_sum += probs[i];
}
if (plfit_walker_alias_sampler_init(&sampler, probs, NUM_ITEMS)) {
return 1;
}
if (plfit_walker_alias_sampler_sample(&sampler, data, NUM_SAMPLES, &rng)) {
return 2;
}
plfit_walker_alias_sampler_destroy(&sampler);
/* Calculate histogram */
for (i = 0; i < NUM_ITEMS; i++) {
hist[i] = 0;
}
for (i = 0; i < NUM_SAMPLES; i++) {
if (data[i] < 0 || data[i] >= NUM_ITEMS) {
printf("Sampled item #%ld out of range: %ld\n", i, data[i]);
return 3;
}
hist[data[i]]++;
}
for (i = 0, max_hist = 0; i < NUM_ITEMS; i++) {
if (hist[i] > max_hist) {
max_hist = hist[i];
}
}
/* Print and test histogram */
for (i = 0; i < NUM_ITEMS; i++) {
printf("%3d: ", (int)i);
j = (int)(hist[i] / ((double)max_hist) * 70);
while (j > 0) {
putchar('#');
j--;
}
printf("\n");
ASSERT_WITHIN_RANGE(hist[i],
(probs[i]/prob_sum - 0.05) * NUM_SAMPLES,
(probs[i]/prob_sum + 0.05) * NUM_SAMPLES);
}
free(data);
data = 0;
return 0;
}
int main(int argc, char* argv[]) {
return test_sampling();
}