/* -*- 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>

#include "test_utilities.h"

int main(void) {

    igraph_integer_t 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;
    igraph_integer_t i, j, n = sizeof(triplets) / sizeof(triplets[0]);
    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++) {
        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 {             \
        printf("Element-wise difference of the following two vectors is too large:\n"); \
        igraph_vector_complex_print(&values);   \
        igraph_vector_complex_print(&values2);  \
    } while(0)

    for (i = 0; i < nodes; i++) {
        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);

    VERIFY_FINALLY_STACK();

    return 0;
}
