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authorKatolaZ <katolaz@freaknet.org>2017-09-27 15:06:31 +0100
committerKatolaZ <katolaz@freaknet.org>2017-09-27 15:06:31 +0100
commit3aee2fd43e3059a699af2b63c6f2395e5a55e515 (patch)
tree58c95505a0906ed9cfa694f9dbd319403fd8f01d /src/ws/ws.c
First commit on github -- NetBunch 1.0
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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 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);
+}