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/* -*- 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;
}
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