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/**
* 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 3 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, see
* <http://www.gnu.org/licenses/>.
*
* (c) Vincenzo Nicosia 2009-2017 -- <v.nicosia@qmul.ac.uk>
*
* This file is part of NetBunch, a package for complex network
* analysis and modelling. For more information please visit:
*
* http://www.complex-networks.net/
*
* If you use this software, please add a reference to
*
* V. Latora, V. Nicosia, G. Russo
* "Complex Networks: Principles, Methods and Applications"
* Cambridge University Press (2017)
* ISBN: 9781107103184
*
***********************************************************************
*
* Implementation of a data structure to maintain a cumulative
* distribution and sample values from it. Used in all the models of
* growing graphs based on some kind of preferential attachment.
*
*/
#include <stdlib.h>
#include <stdio.h>
#include "cum_distr.h"
cum_distr_t* cum_distr_init(unsigned int N){
cum_distr_t* d = NULL;
d = malloc(sizeof(cum_distr_t));
d->N = N;
d->num = 0;
d->sum = 0;
d->v = malloc((d->N) * sizeof(idval_t));
return d;
}
int cum_distr_add(cum_distr_t *d, unsigned int id, long double val){
idval_t *tmp;
if (d->num == d->N){
//fprintf(stderr, "+++++++++ REALLOC ++++++++++\n");
d->N += 10;
tmp = realloc(d->v, d->N * sizeof(idval_t));
if (!tmp){
d->N -= 10;
fprintf(stderr, "#### Error!!! Unable to add more values to the cumulative distribution!!!\n");
return -1;
}
else{
d->v = tmp;
}
}
d->sum += val;
d->v[d->num].id = id;
d->v[d->num].value = d->sum;
d->num += 1;
//fprintf(stderr, ">>>>>> update >>>>>> d->num: %d\n", d->num);
return 0;
}
/* sample an id from the cumulative distribution, by means of binary
search */
unsigned int cum_distr_sample(cum_distr_t *d){
long double val;
unsigned int high, low, cur;
val = d->sum * rand() / RAND_MAX;
cur = d->num / 2;
low = 0;
high = d->num - 1;
while (low < high){
if (d->v[cur].value < val){
low = cur+1;
}
else if(d->v[cur].value >= val){
high = cur;
}
cur = (high + low) / 2;
}
return d->v[cur].id;
}
void cum_distr_dump(cum_distr_t *d){
unsigned int i;
for(i=0; i< d->num; i++){
fprintf(stderr, "(%d, %g)\n", d->v[i].id, (double)(d->v[i].value));
}
}
void cum_distr_destroy(cum_distr_t *d){
free(d->v);
free(d);
}
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