First commit on github -- NetBunch 1.0

1 files changed, 259 insertions, 0 deletions

diff --git a/src/conf/conf_model_deg.c b/src/conf/conf_model_deg.c
new file mode 100644
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+++ b/src/conf/conf_model_deg.c
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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 simple graph (i.e., without self-loops
+ *  and/or multiple edges) from the configuration model, using the
+ *  degree sequence provided as input.
+ *
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "utils.h"
+#include "iltree_double.h"
+
+
+#define MAXREJECTS 1000000
+
+
+/* Usage */
+void usage(char *argv[]){
+  printf("********************************************************************\n"
+         "**                                                                **\n"
+         "**                   -*-  conf_model_deg  -*-                     **\n"
+         "**                                                                **\n"
+         "**  Sample a simple graph from the configuration model associated **\n"
+         "**  to the degree sequence provided as input.                     **\n"
+         "**                                                                **\n"
+         "**  The degree sequence is a file with format:                    **\n"
+         "**                                                                **\n"
+         "**                           k_1                                  **\n"
+         "**                           k_2                                  **\n"
+         "**                           k_3                                  **\n"
+         "**                           ....                                 **\n"
+         "**                           k_N                                  **\n"
+         "**                                                                **\n"
+         "**   where 'k_i' is the degree of the i-th node. The program      **\n"
+         "**   prints on output the edge-list of the resulting graph.       **\n"
+         "**                                                                **\n"
+         "**   The second (optional) parameter 'threshold' indicates the    **\n"
+         "**   number of edge stubs that are allowed to remain unmatched    **\n"
+         "**   in the final graph. This parameter might be used to          **\n"
+         "**   obtain a graph from a too-constrained degree sequence, e.g., **\n"
+         "**   a power-law sequence whose maximum degree is larger than     **\n"
+         "**   the structural cut-off.                                      **\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"
+         " Please visit http://www.complex-networks.net for more information\n\n"
+         " (c) Vincenzo Nicosia 2010-2017 (v.nicosia@qmul.ac.uk)\n"
+         "********************************************************************\n\n"
+         );
+  printf("Usage: %s <degs> [<threshold>]\n\n" , argv[0]);
+}
+
+
+unsigned int count_stubs(unsigned int *nodes, int N){
+  
+  int i;
+  unsigned int cnt;
+
+  cnt = 0;
+  for (i=0; i<N; i ++){
+    cnt += nodes[i];
+  }
+  return cnt;
+}
+
+
+void sample_graph_conf(unsigned int *nodes, int N, iltree_t *t, 
+                           unsigned int thresh){
+  
+  unsigned int S;
+  unsigned int i, j;
+  unsigned int n_stubs;
+  unsigned int *stubs;
+  unsigned int countreject;
+  unsigned int L1, L2, I1, I2, tmp;
+  long double k;
+  FILE *tmp_file;
+  
+  n_stubs = count_stubs(nodes, N);
+  
+  if (n_stubs %2){
+    fprintf(stderr, "The sequence is not even!\n");
+    exit(3);
+  }
+  /* ind = malloc(n_stubs * sizeof(unsigned int)); */
+  /* stub2node = malloc(n_stubs * sizeof(unsigned int)); */
+  
+  stubs = malloc(n_stubs * sizeof(unsigned int));
+  
+  
+  do{
+    countreject = 0;
+    S = 0;
+    /*
+     * We first initialize the stubs
+     *
+     * This is needed only before the first iteration, indeed.... 
+     *
+     */
+    for(i=0; i<N; i ++){
+      for(j=0; j<nodes[i]; j ++){
+        stubs[S] = i;
+        S += 1;
+      }
+    }
+    while (S > 0 && countreject < MAXREJECTS){
+      /* sample the first stub */
+      L1 = rand() % S;
+      I1 = stubs[L1];
+      S -= 1;
+
+      /* sample the second stub */
+      L2 = rand() % S;
+      I2 = stubs[L2];
+      S -= 1;
+
+      if (L1 == L2){/* If L1 and L2 are the same element, discard the
+                       sample */
+        /* reset S to the value it had before */
+        S += 2;
+        continue;
+      }
+      
+      if (I1 == I2){
+        /* reject the pair: it's the same node! */
+        countreject += 1;
+        /* reset S to the value it had before */
+        S += 2;
+        continue;
+      }
+      
+    
+      if (I1 > I2){ /* we require that I1 < I2 */
+        tmp = I2;
+        I2 = I1;
+        I1 = tmp;
+      }
+      k = 1.0 * (I2)* (I2-1) / 2 + I1 + 1; /* This number represents the
+                                        couple I1, I2 (I1 < I2)*/
+      if (!iltree_lookup(*t, &k)){ /* The element "k" is not yet present in the BST*/
+        /* We can accept the new pair... */
+        /* ...so we insert it into the tree */
+        iltree_insert(*t, &k);
+        /* remove the two stubs */
+        tmp = stubs[L1];
+        stubs[L1] = stubs[S+1];
+        stubs[S+1] = tmp;
+
+        tmp = stubs[L2];
+        stubs[L2] = stubs[S];
+        stubs[S] = tmp;
+      }
+      else{/* reject the pair */
+        /* reset S to the value it had before */
+        countreject += 1;
+        S += 2;
+      }
+    }
+    
+    /* Let's check if we got a graph....*/
+    if (countreject >= MAXREJECTS){
+      if (S <= thresh){
+        fprintf(stderr, "Found a graph (unmatched stubs: %d <= threshold: %d)\n", 
+                S, thresh);
+        break;
+      }
+      else{
+        fprintf(stderr, "Graph not found (unmatched stubs: %d > threshold: %d)\n", 
+                S, thresh);
+        S = 0;
+        countreject = 0;
+        tmp_file = iltree_get_fileout(*t);
+        iltree_destroy(*t);
+        *t = NULL;
+        *t = iltree_double_init(*t, tmp_file);
+      }
+    }
+    else{
+      fprintf(stderr, "Found a graph!\n");
+      break;
+    }
+  } while(1);
+  free(stubs);
+}
+
+
+
+int main(int argc, char *argv[]){
+  
+  unsigned int  *nodes= NULL;
+  int N;
+  iltree_t t = NULL;
+  FILE *filein;
+  unsigned int thresh;
+
+  if (argc < 2){
+    usage(argv);
+    exit(1);
+  }
+  
+  srand(time(NULL));
+
+  if (!strcmp(argv[1], "-")){
+    /* take the input from STDIN */
+    filein = stdin;
+  }
+  else {
+    filein = openfile_or_exit(argv[1], "r", 2);
+  }
+  
+  if (argc > 2) /* Set the threshold */
+    thresh = atoi(argv[2]);
+  else
+    thresh = 0;
+  
+  
+  t = iltree_double_init(t, stdout);
+  
+  N = read_deg_seq(filein, &nodes);
+  sample_graph_conf(nodes, N, &t, thresh);
+  iltree_double_dump_edges(t);
+  fclose(filein);
+  free(nodes);
+  iltree_destroy(t);
+}