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Diffstat (limited to 'src/ba/ba.c')
| -rw-r--r-- | src/ba/ba.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/src/ba/ba.c b/src/ba/ba.c new file mode 100644 index 0000000..e395d6d --- /dev/null +++ b/src/ba/ba.c @@ -0,0 +1,185 @@ +/** + * 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); +} |