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/* -*- mode: C -*- */
/*
IGraph library.
Copyright (C) 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>
#include <time.h>
#define DIM 10
int check_ev(const igraph_matrix_t *A, const igraph_vector_t *values,
const igraph_matrix_t *vectors, int err_off) {
int i, n=igraph_matrix_nrow(A);
int ne=igraph_matrix_ncol(vectors);
igraph_vector_t v, lhs, rhs;
if (ne != igraph_vector_size(values)) {
printf("'values' and 'vectors' sizes do not match\n");
exit(err_off + 1);
}
igraph_vector_init(&lhs, n);
igraph_vector_init(&rhs, n);
for (i=0; i<ne; i++) {
igraph_vector_view(&v, &MATRIX(*vectors, 0, i), n);
igraph_blas_dgemv(/*transpose=*/ 0, /*alpha=*/ 1, A, &v,
/*beta=*/ 0, &lhs);
igraph_vector_update(&rhs, &v);
igraph_vector_scale(&rhs, VECTOR(*values)[i]);
if (igraph_vector_maxdifference(&lhs, &rhs) > 1e-10) {
printf("LHS %i: ", i); igraph_vector_print(&lhs);
printf("RHS %i: ", i); igraph_vector_print(&rhs);
exit(err_off + 2);
}
}
igraph_vector_destroy(&rhs);
igraph_vector_destroy(&lhs);
return 0;
}
int main() {
igraph_matrix_t A;
igraph_vector_t values;
igraph_matrix_t vectors;
int i, j;
igraph_eigen_which_t which;
igraph_arpack_options_t options;
igraph_rng_seed(igraph_rng_default(), 42 * 42);
igraph_matrix_init(&A, DIM, DIM);
igraph_matrix_init(&vectors, 0, 0);
igraph_vector_init(&values, 0);
igraph_arpack_options_init(&options);
for (i=0; i<DIM; i++) {
for (j=i; j<DIM; j++) {
MATRIX(A, i, j) = MATRIX(A, j, i) =
igraph_rng_get_integer(igraph_rng_default(), 1, 10);
}
}
which.pos=IGRAPH_EIGEN_LM;
which.howmany=2;
igraph_eigen_matrix_symmetric(&A, /*sA=*/ 0, /*fun=*/ 0, DIM, /*extra=*/ 0,
IGRAPH_EIGEN_ARPACK, &which, &options,
/*storage=*/ 0, &values, &vectors);
igraph_vector_print(&values);
check_ev(&A, &values, &vectors, 0);
which.howmany=8;
igraph_eigen_matrix_symmetric(&A, /*sA=*/ 0, /*fun=*/ 0, DIM, /*extra=*/ 0,
IGRAPH_EIGEN_ARPACK, &which, &options,
/*storage=*/ 0, &values, &vectors);
igraph_vector_print(&values);
check_ev(&A, &values, &vectors, 10);
which.pos=IGRAPH_EIGEN_BE;
which.howmany=5;
igraph_eigen_matrix_symmetric(&A, /*sA=*/ 0, /*fun=*/ 0, DIM, /*extra=*/ 0,
IGRAPH_EIGEN_ARPACK, &which, &options,
/*storage=*/ 0, &values, &vectors);
igraph_vector_print(&values);
check_ev(&A, &values, &vectors, 20);
which.pos=IGRAPH_EIGEN_SM;
which.howmany=5;
igraph_eigen_matrix_symmetric(&A, /*sA=*/ 0, /*fun=*/ 0, DIM, /*extra=*/ 0,
IGRAPH_EIGEN_ARPACK, &which, &options,
/*storage=*/ 0, &values, &vectors);
igraph_vector_print(&values);
check_ev(&A, &values, &vectors, 30);
igraph_vector_destroy(&values);
igraph_matrix_destroy(&vectors);
igraph_matrix_destroy(&A);
return 0;
}
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