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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/er/er_B.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 samples a graph from the Erdos-Renyi random graph
+ * model B, i.e., the ensemble of graphs with N nodes where each of
+ * the possible N(N-1)/2 edges is created with probability equal to
+ * p, and independently from all the other edges.
+ *
+ *
+ * References:
+ *
+ * [1] Erdős, P. & Rényi, A. On Random Graphs I Publ. Math. Debrecen,
+ * 6, 290 (1959)
+ *
+ * [2] Erdos, P. & Renyi, A. On the evolution of random graphs
+ * Publ. Math. Inst. Hungary. Acad. Sci., 5, 17-61 (1960)
+ *
+ */
+
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+
+void usage(char *argv[]){
+ printf("********************************************************************\n"
+ "** **\n"
+ "** -*- er_B -*- **\n"
+ "** **\n"
+ "** sample an Erdos-Renyi graph of N nodes and edge probability p **\n"
+ "** **\n"
+ "** the output is an I,J matrix: **\n"
+ "** I_1 J_1 **\n"
+ "** I_2 J_2 **\n"
+ "** I_3 J_3 **\n"
+ "** ... ... **\n"
+ "** I_K J_K **\n"
+ "** **\n"
+ "** (output is to stdout or to a file) **\n"
+ "** **\n"
+ "** If a filename is specified as fourth parameter then **\n"
+ "** the degree sequence is dumped out to that file **\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> <p> [<filout>]\n\n" , argv[0]);
+}
+
+
+
+int main(int argc, char *argv[]){
+
+ unsigned int N, i, j;;
+ FILE *fileout;
+ double p, val;
+ char error_str [256];
+
+ if(argc < 3){
+ usage(argv);
+ exit(1);
+ }
+
+ N = atoi(argv[1]);
+ p = atof(argv[2]);
+
+
+ if (argc >3){
+ fileout = fopen(argv[3], "w+");
+ if (!fileout){
+ sprintf(error_str, "Error opening file %s", argv[3]);
+ perror(error_str);
+ exit(2);
+ }
+ }
+ else{
+ fileout = stdout;
+ }
+
+ srand(time(NULL));
+
+ /* Loop over all nodes...*/
+ for(i=0; i<N; i++){
+ /* Loop over the nodes with label larger than i...*/
+ for(j=i+1; j<N; j++){
+ val = rand() * 1.0 / RAND_MAX;
+ /* if the sample is smaller than p, create the edge */
+ if (val < p){
+ fprintf(fileout, "%d %d\n", i, j);
+ }
+ }
+ }
+ fclose(fileout);
+}