/* -*- 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() {
  
  int nodes=10;
  igraph_real_t triplets[] = { 1,0, 1/4.0,       0,1, 1/3.0, 
			       2,0, 1/4.0,       0,2, 1/3.0,
			       3,0, 1.0,         0,3, 1/3.0,
			       4,1, 1.0,         1,4, 1/4.0,
			       5,1, 1.0,         1,5, 1/4.0,
			       6,1, 1.0,         1,6, 1/4.0,
			       7,2, 1.0,         2,7, 1/4.0,
			       8,2, 1.0,         2,8, 1/4.0,
			       9,2, 1.0,         2,9, 1/4.0 };
  
  igraph_sparsemat_t mat;
  int i, n=sizeof(triplets) / sizeof(igraph_real_t);
  igraph_eigen_which_t which;
  igraph_vector_complex_t values, values2;
  igraph_matrix_complex_t vectors, vectors2;
  igraph_matrix_t mat2;
  
  igraph_sparsemat_init(&mat, nodes, nodes, n/3);
  for (i=0; i<n; i+=3) {
    igraph_sparsemat_entry(&mat, triplets[i], triplets[i+1], triplets[i+2]);
  }

  which.pos=IGRAPH_EIGEN_LM;
  which.howmany=1;

  igraph_vector_complex_init(&values, 0);
  igraph_matrix_complex_init(&vectors, 0, 0);

  igraph_eigen_matrix(/*matrix=*/ 0, /*sparsemat=*/ &mat, /*fun=*/ 0, 
		      nodes, /*extra=*/ 0, IGRAPH_EIGEN_LAPACK, &which, 
		      /*options=*/ 0, /*storage=*/ 0, &values, &vectors);

  if (IGRAPH_REAL(MATRIX(vectors, 0, 0)) < 0) { 
    igraph_matrix_complex_scale(&vectors, igraph_complex(-1.0, -0.0 ));
  }

  igraph_vector_complex_print(&values);
  igraph_matrix_complex_print(&vectors);

  igraph_sparsemat_destroy(&mat);

  /* Calcualate all eigenvalues, using SM and LM and then check that they 
     are the same, in opposite order. We use a random matrix this time. */
  
  igraph_rng_seed(igraph_rng_default(), 42);
  igraph_matrix_init(&mat2, nodes, nodes);
  for (i=0; i<nodes; i++) {
    int j;
    for (j=0; j<nodes; j++) {
      MATRIX(mat2, i, j) = igraph_rng_get_integer(igraph_rng_default(), 1, 10);
    }
  }
  
  which.pos=IGRAPH_EIGEN_LM;
  which.howmany=nodes;
  igraph_eigen_matrix(&mat2, /*sparsemat=*/ 0, /*fun=*/ 0, nodes, 
		      /*extra=*/ 0, IGRAPH_EIGEN_LAPACK, &which, 
		      /*options=*/ 0, /*storage=*/ 0, &values, &vectors);
  
  which.pos=IGRAPH_EIGEN_SM;
  which.howmany=nodes;
  igraph_vector_complex_init(&values2, 0);
  igraph_matrix_complex_init(&vectors2, 0, 0);
  igraph_eigen_matrix(&mat2, /*sparsemat=*/ 0, /*fun=*/ 0, nodes, 
		      /*extra=*/ 0, IGRAPH_EIGEN_LAPACK, &which, 
		      /*options=*/ 0, /*storage=*/ 0, &values2, &vectors2);

#define DUMP() do {				\
    igraph_vector_complex_print(&values);	\
    igraph_vector_complex_print(&values2);	\
  } while(0)

  for (i=0; i<nodes; i++) { 
    int j;
    igraph_real_t d=
      igraph_complex_abs(igraph_complex_sub(VECTOR(values)[i],
					    VECTOR(values2)[nodes-i-1]));
    if (d > 1e-15) { DUMP(); return 2; }
    for (j=0; j<nodes; j++) { 
      igraph_real_t d=
	igraph_complex_abs(igraph_complex_sub(MATRIX(vectors, j, i), 
					      MATRIX(vectors2, j,
						     nodes-i-1)));
      if (d > 1e-15) { DUMP(); return 3; }
    }
  }
  
  igraph_vector_complex_destroy(&values);
  igraph_matrix_complex_destroy(&vectors);  
  igraph_vector_complex_destroy(&values2);
  igraph_matrix_complex_destroy(&vectors2);

  igraph_matrix_destroy(&mat2);

  return 0;
}
