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Diffstat (limited to 'src/ws/ws.c')
| -rw-r--r-- | src/ws/ws.c | 204 |
1 files changed, 204 insertions, 0 deletions
diff --git a/src/ws/ws.c b/src/ws/ws.c new file mode 100644 index 0000000..bfbe102 --- /dev/null +++ b/src/ws/ws.c @@ -0,0 +1,204 @@ +/** + * 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 creates a network using the Watts-Strogatz + * small-world network model. + * + * References: + * + * D. J. Watts and S. H. Strogatz. "Collective dynamics of + * 'small-world' networks". Nature 393 (1998), 440–442. + * + * + */ + + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <time.h> + +#include "utils.h" + +void usage(char *argv[]){ + printf("********************************************************************\n" + "** **\n" + "** -*- ws -*- **\n" + "** **\n" + "** Create a graph with 'N' nodes, using the Watts-Strogatz **\n" + "** small-world network model. The algorithm starts from a **\n" + "** circle graph with 'N' nodes and m*N edges, i.e. by putting **\n" + "** the 'N' nodes around a circle, so that each node is **\n" + "** connected to the 'm' closest nodes in the circle on each **\n" + "** direction. Then, each edge is rewired at random with **\n" + "** probability equal to 'p'. **\n" + "** **\n" + "** The output is an edge list in the format: **\n" + "** **\n" + "** I_1 J_1 **\n" + "** I_2 J_2 **\n" + "** I_3 J_3 **\n" + "** ... ... **\n" + "** I_K J_K **\n" + "** **\n" + "** If 'SHOW' is specified as a fourth parameter, the program **\n" + "** prints on STDERR the number of edges that were actually **\n" + "** rewired. **\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> <p> [SHOW]\n\n" , argv[0]); +} + + + +/** + * + * This function checks if j is a neighbour of i, looking into the + * m positions of J starting at i*m + * + * In practice, the assumption is that J contains the m neighbours of + * node 0 in the first m positions, then the m neighbours of node 1, + * and to forth + * + */ + +int __ws_is_neigh(unsigned int i, unsigned int j, unsigned int *J, unsigned int m){ + + int k; + + for(k = i*m; k< (i+1)*m; k++){ + if (J[k] == j) + return 1; + } + return 0; +} + + +int create_circle(unsigned int N, unsigned int m, unsigned int **J){ + + int K; + int i, j, l; + + K = N *m; + + *J = malloc(K * sizeof(unsigned int)); + + K = 0; + + for(i=0; i<N; i++){ + for(j=0; j < m; j++){ + l = (i + j + 1) % N; + (*J)[K] = l; + K += 1; + } + } + return K; +} + + + +int ws(unsigned int *J, unsigned int N, unsigned int m, double p){ + + unsigned int i, j, l, l1, num_rewire; + + double xi; + + num_rewire = 0; + + for(i=0; i<N; i++){ + for(j=0; j<m; j++){ + l = (i+j) % N; + xi = 1.0 * rand() / RAND_MAX; + if (xi < p){ + l1 = (int)(rand() % N); + if( (l1 != i) && + (l1 != l) && + !(__ws_is_neigh(i, l1, J, m))){ + /* replace (i,l) with (i,l1) */ + J[m * i + j] = l1; + num_rewire += 1; + } + else{ + /* do nothing */ + } + } + } + } + return num_rewire; +} + + +void dump_edges(unsigned int *J, unsigned int N, unsigned int m){ + + int i, j; + + for(i=0; i<N; i++){ + for(j=0; j<m; j++){ + printf("%d %d\n", i, J[(m*i)+j]); + } + } +} + + +int main(int argc, char *argv[]){ + + int N, m, num_rewire; + unsigned int *J; + double p; + + if(argc < 4){ + usage(argv); + exit(1); + } + + J = NULL; + + N = atoi(argv[1]); + m = atoi(argv[2]); + p = atof(argv[3]); + + create_circle(N, m, &J); + + + srand(time(NULL)); + + num_rewire = ws(J, N, m, p); + if (argc > 4 && !my_strcasecmp("SHOW", argv[4])){ + fprintf(stderr, "Rewired edges: %d\n", num_rewire); + } + dump_edges(J, N, m); + free(J); +} |