text: /* -*- mode: C -*-  */
  /* 
     IGraph library.
     Copyright (C) 2006-2012  Gabor Csardi <csardi.gabor@gmail.com>
     334 Harvard street, Cambridge, MA 02139 USA
     
     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 2 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, write to the Free Software
     Foundation, Inc.,  51 Franklin Street, Fifth Floor, Boston, MA 
     02110-1301 USA
  
  */
  
  #include <igraph.h>
  
  void show_results(igraph_t *g, igraph_vector_t *mod, igraph_matrix_t *merges, FILE* f) {
    long int i;
    igraph_vector_t membership;
  
    igraph_vector_init(&membership, 0);
  
    i=igraph_vector_which_max(mod);
    fprintf(f, "Modularity:  %f\n", VECTOR(*mod)[i]);
    igraph_community_to_membership(merges, igraph_vcount(g), i, &membership, 0);
    printf("Membership: ");
    for (i=0; i<igraph_vector_size(&membership); i++) {
      printf("%li ", (long int)VECTOR(membership)[i]);
    }
    printf("\n");
  
    igraph_vector_destroy(&membership);
  }
  
  int main() {
    igraph_t g;
    igraph_vector_t modularity, weights;
    igraph_matrix_t merges;
    FILE *f;
  
    igraph_vector_init(&modularity,0);
    igraph_matrix_init(&merges,0,0);
    igraph_vector_init(&weights,0);
  
    /* Simple unweighted graph */
    igraph_small(&g, 10, IGRAPH_UNDIRECTED, 
  	       0,1,0,2,0,3,0,4, 1,2,1,3,1,4, 2,3,2,4, 3,4,
  	       5,6,5,7,5,8,5,9, 6,7,6,8,6,9, 7,8,7,9, 8,9,
             0,5, -1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
  
    /* Same simple graph, with uniform edge weights */
    igraph_vector_resize(&weights, igraph_ecount(&g));
    igraph_vector_fill(&weights, 2);
    igraph_community_fastgreedy(&g, &weights, &merges, &modularity, 
  			      /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
    igraph_destroy(&g);
  
    /* Simple nonuniform weighted graph, with and without weights */
    igraph_small(&g, 6, IGRAPH_UNDIRECTED, 
  	       0,1,1,2,2,3,2,4,2,5,3,4,3,5,4,5, -1);
    igraph_vector_resize(&weights, 8);
    igraph_vector_fill(&weights, 1);
    VECTOR(weights)[0] = 10; VECTOR(weights)[1] = 10;
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
    igraph_community_fastgreedy(&g, &weights, &merges, &modularity, 
  			      /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
    igraph_destroy(&g);
  
    /* Zachary Karate club */
    igraph_small(&g, 0, IGRAPH_UNDIRECTED, 
  	       0,  1,  0,  2,  0,  3,  0,  4,  0,  5,
  	       0,  6,  0,  7,  0,  8,  0, 10,  0, 11,
  	       0, 12,  0, 13,  0, 17,  0, 19,  0, 21,
  	       0, 31,  1,  2,  1,  3,  1,  7,  1, 13,
  	       1, 17,  1, 19,  1, 21,  1, 30,  2,  3,
  	       2,  7,  2,  8,  2,  9,  2, 13,  2, 27,
  	       2, 28,  2, 32,  3,  7,  3, 12,  3, 13,
  	       4,  6,  4, 10,  5,  6,  5, 10,  5, 16,
  	       6, 16,  8, 30,  8, 32,  8, 33,  9, 33,
  	       13, 33, 14, 32, 14, 33, 15, 32, 15, 33,
  	       18, 32, 18, 33, 19, 33, 20, 32, 20, 33,
  	       22, 32, 22, 33, 23, 25, 23, 27, 23, 29,
  	       23, 32, 23, 33, 24, 25, 24, 27, 24, 31,
  	       25, 31, 26, 29, 26, 33, 27, 33, 28, 31,
  	       28, 33, 29, 32, 29, 33, 30, 32, 30, 33,
  	       31, 32, 31, 33, 32, 33,
  	       -1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, 
  			      /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
    igraph_destroy(&g);
     
    /* Simple disconnected graph with isolates */
    igraph_small(&g, 9, IGRAPH_UNDIRECTED,
  	       0,  1,  0,  2,  0,  3,  1,  2,  1,  3,  2,  3,
  	       4,  5,  4,  6,  4,  7,  5,  6,  5,  7,  6,  7,
  	       -1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout); 
    igraph_destroy(&g);
  
    /* Disjoint union of two rings */
    igraph_small(&g, 20, IGRAPH_UNDIRECTED,
             0,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,0,9,
  	   10,11,11,12,12,13,13,14,14,15,15,16,16,17,17,18,18,19,10,19,-1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout);
    igraph_destroy(&g);
  
    /* Completely empty graph */
    igraph_small(&g, 10, IGRAPH_UNDIRECTED, -1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout);
    igraph_destroy(&g);
  
    /* Ring graph with loop edges */
    igraph_small(&g, 6, IGRAPH_UNDIRECTED,
            0,1,1,2,2,3,3,4,4,5,5,0,0,0,2,2,-1);
    igraph_community_fastgreedy(&g, 0, &merges, &modularity, /*membership=*/ 0);
    show_results(&g, &modularity, &merges, stdout);
    igraph_destroy(&g);
  
    igraph_vector_destroy(&modularity);
    igraph_vector_destroy(&weights);
    igraph_matrix_destroy(&merges);
  
    return 0;
  }
  