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/* -*- mode: C -*- */
/*
IGraph library.
Copyright (C) 2011-2012 Gabor Csardi <csardi.gabor@gmail.com>
334 Harvard st, Cambridge, MA, 02138 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>
#define SIZE (1000)
int main() {
igraph_matrix_t M, M2;
igraph_vector_t lambda;
igraph_matrix_t V;
igraph_vector_t groups;
igraph_vector_t ivec;
int i, j;
int n;
igraph_rng_seed(igraph_rng_default(), 42);
/* Symmetric matrix, exponentially distributed elements */
igraph_matrix_init(&M, SIZE, SIZE);
n=igraph_matrix_nrow(&M);
for (i=0; i<n; i++) {
for (j=0; j<n; j++) {
MATRIX(M, i, j) = igraph_rng_get_exp(igraph_rng_default(), 1);
}
}
igraph_matrix_init(&M2, n, n);
igraph_matrix_update(&M2, &M);
igraph_matrix_transpose(&M2);
igraph_matrix_add(&M, &M2);
igraph_matrix_scale(&M, 0.5);
igraph_matrix_destroy(&M2);
/* Get first (most positive) two eigenvectors */
igraph_vector_init(&lambda, 0);
igraph_matrix_init(&V, 0, 0);
igraph_lapack_dsyevr(&M, IGRAPH_LAPACK_DSYEV_SELECT, /*vl=*/ 0, /*vu=*/ 0,
/*vestimate=*/ 0, /*il=*/ n-1, /*iu=*/ n,
/*abstol=*/ 0.0, /*values=*/ &lambda, /*vectors=*/ &V,
/*support=*/ 0);
/* Grouping */
igraph_vector_init(&groups, 0);
igraph_vector_init(&ivec, 2);
VECTOR(ivec)[0] = 2; VECTOR(ivec)[1] = 3;
igraph_scg_grouping(&V, &groups, /*invervals=*/ 0,
/*intervals_vector=*/ &ivec, IGRAPH_SCG_SYMMETRIC,
IGRAPH_SCG_OPTIMUM, /*p=*/ 0, /*maxiter=*/ 100);
igraph_vector_print(&groups);
igraph_vector_destroy(&ivec);
igraph_vector_destroy(&groups);
igraph_vector_destroy(&lambda);
igraph_matrix_destroy(&V);
igraph_matrix_destroy(&M);
return 0;
}
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