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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
*
***********************************************************************
*
*
* This program grows a network with N nodes using the linear
* preferential attachment model proposed by Barabasi and
* Albert. Each new node creates m links, and the initial (seed)
* network is a ring of n0>=m nodes.
*
*
* References:
*
* [1] A.-L. Barabasi, R. Albert, "Emergence of scaling in random
* networks", Science 286, 509-512 (1999).
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
void usage(char *argv[]){
printf("********************************************************************\n"
"** **\n"
"** -*- ba -*- **\n"
"** **\n"
"** Grow a scale-free network of 'N' nodes using the linear **\n"
"** preferential attachment model (Barabasi-Albert). **\n"
"** The initial network is a ring of 'n0' nodes, and each new **\n"
"** node creates 'm' edges. **\n"
"** **\n"
"** The program prints on STDOUT the edge-list of the final **\n"
"** graph. **\n"
"** **\n"
"********************************************************************\n"
" This is Free Software - You can use and distribute it under \n"
" the terms of the GNU General Public License, version 3 or later\n\n"
" (c) Vincenzo Nicosia 2010-2017 (v.nicosia@qmul.ac.uk)\n\n"
"********************************************************************\n\n"
);
printf("Usage: %s <N> <m> <n0>\n", argv[0]);
}
int init_network(unsigned int **S, unsigned int n0){
int n;
for(n=0; n<n0; n++){
S[0][n] = n;
S[1][n] = (n+1) % n0;
}
return n;
}
int select_neighbour(unsigned int **S, unsigned int S_num){
int d;
d = rand()%(S_num * 2);
if (d < S_num)
return S[0][d];
else{
return S[1][d-S_num];
}
}
/* check if 'd' is already a neighbour of 'i' */
int already_neighbour(unsigned int **S, unsigned int S_num, unsigned int j, unsigned int d){
int i;
for(i=S_num; i< S_num + j; i ++){
if (S[1][i] == d)
return 1;
}
return 0;
}
unsigned int grow_ba_network(unsigned int **S, unsigned int N,
unsigned int m, unsigned int n0, unsigned int S_num){
int i, j;
int n, d;
for(i=0; i<N-n0; i++){
/* Let's add a new node */
n = n0 + i; /* This is the id of the new node */
for(j=0; j<m; j++){
S[0][S_num+j] = n;
d = select_neighbour(S, S_num);
while(already_neighbour(S, S_num, j, d)){
d = select_neighbour(S, S_num);
}
S[1][S_num + j] = d;
}
S_num += m;
}
return S_num;
}
int main(int argc, char *argv[]){
unsigned int **S;
unsigned int S_num, S_size, i;
int m, n0, N;
if (argc < 4){
usage(argv);
exit(1);
}
srand(time(NULL));
N = atoi(argv[1]);
m = atoi(argv[2]);
n0 = atoi(argv[3]);
S_size = (N+n0) * m ;
if (N < 1){
fprintf(stderr, "N must be positive\n");
exit(1);
}
if(m > n0){
fprintf(stderr, "n0 cannot be smaller than m\n");
exit(1);
}
if (n0<1){
fprintf(stderr, "n0 must be positive\n");
exit(1);
}
if (m < 1){
fprintf(stderr, "m must be positive\n");
exit(1);
}
S = malloc(2 * sizeof(unsigned int*));
S[0] = malloc(S_size * sizeof(unsigned int));
S[1] = malloc(S_size * sizeof(unsigned int));
S_num = init_network(S, n0);
S_num = grow_ba_network(S, N, m, n0, S_num);
for(i=0; i<S_num; i ++){
printf("%d %d\n",S[0][i], S[1][i]);
}
free(S[0]);
free(S[1]);
free(S);
}
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