/* -*- mode: C -*-  */
/* 
   IGraph library.
   Copyright (C) 2011-2012  Gabor Csardi <csardi.gabor@gmail.com>
   334 Harvard st, 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>

int main() {

  igraph_t g;
  igraph_matrix_t L, R;
  igraph_sparsemat_t Lsparse, Rsparse;
  igraph_matrix_t adj, V;
  igraph_vector_t groups;
  igraph_eigen_which_t which;

  igraph_matrix_init(&L, 0, 0);
  igraph_matrix_init(&R, 0, 0);
  igraph_matrix_init(&adj, 0, 0);
  igraph_matrix_init(&V, 0, 0);
  igraph_vector_init(&groups, 0);
    
  igraph_rng_seed(igraph_rng_default(), 42);
  
  igraph_tree(&g, 10, /* children= */ 3, IGRAPH_TREE_UNDIRECTED);
  
  igraph_get_adjacency(&g, &adj, IGRAPH_GET_ADJACENCY_BOTH, /*eids=*/ 0);

  which.pos=IGRAPH_EIGEN_LM;
  which.howmany=1;
  igraph_eigen_matrix_symmetric(&adj, /*sparsemat=*/ 0, /*fun=*/ 0,
				igraph_vcount(&g), /*extra=*/ 0, 
				/*algorithm=*/ IGRAPH_EIGEN_LAPACK,
				&which, /*options=*/ 0, /*storage=*/ 0, 
				/*values=*/ 0, &V);

#define SEMI()								\
  do {									\
    igraph_scg_semiprojectors(&groups, IGRAPH_SCG_SYMMETRIC, &L, &R,	\
			      &Lsparse, &Rsparse, /*p=*/ 0,		\
			      IGRAPH_SCG_NORM_ROW);			\
  } while(0)

#define PRINTRES()				\
  do {						\
    printf("----------------------\n");		\
    igraph_matrix_print(&L);			\
    printf("---\n");				\
    igraph_matrix_print(&R);			\
    printf("---\n");				\
  } while (0)

  /* -------------- */

  igraph_scg_grouping(&V, &groups, /*intervals=*/ 3, 
		      /*intervals_vector=*/ 0, IGRAPH_SCG_SYMMETRIC,
		      IGRAPH_SCG_OPTIMUM, /*p=*/ 0, /*maxiter=*/ 10000);
  SEMI();
  PRINTRES();

  /* -------------- */

  igraph_scg_grouping(&V, &groups, /*intervals=*/ 2, 
		      /*intervals_vector=*/ 0, IGRAPH_SCG_SYMMETRIC,
		      IGRAPH_SCG_INTERV_KM, /*p=*/ 0, /*maxiter=*/ 10000);
  SEMI();
  PRINTRES();

  /* -------------- */

  igraph_scg_grouping(&V, &groups, /*intervals=*/ 2, 
		      /*intervals_vector=*/ 0, IGRAPH_SCG_SYMMETRIC,
		      IGRAPH_SCG_INTERV, /*p=*/ 0, /*maxiter=*/ 10000);
  SEMI();
  PRINTRES();

  /* -------------- */

  igraph_scg_grouping(&V, &groups, /*(ignored) intervals=*/ 0, 
		      /*intervals_vector=*/ 0, IGRAPH_SCG_SYMMETRIC,
		      IGRAPH_SCG_EXACT, /*p=*/ 0, /*maxiter=*/ 10000);
  SEMI();
  PRINTRES();

  /* -------------- */

  igraph_vector_destroy(&groups);
  igraph_matrix_destroy(&V);
  igraph_matrix_destroy(&adj);
  igraph_destroy(&g);
  
  return 0;
}