int main() {
igraph_matrix_t A;
igraph_matrix_t values, vectors;
igraph_arpack_options_t options;
cb2_data_t data = { &A };
int i, j;
igraph_rng_seed(igraph_rng_default(), 42 * 42);
igraph_matrix_init(&A, DIM, DIM);
for (i=0; i<DIM; i++) {
for (j=0; j<DIM; j++) {
MATRIX(A, i, j) = igraph_rng_get_integer(igraph_rng_default(), -10, 10);
}
}
igraph_arpack_options_init(&options);
options.n=DIM;
options.start=0;
options.nev=4;
options.ncv=9;
options.which[0]='L' ; options.which[1]='M';
igraph_matrix_init(&values, 0, 0);
igraph_matrix_init(&vectors, options.n, 1);
igraph_arpack_rnsolve(cb2, /*extra=*/ &data, &options, /*storage=*/ 0,
&values, &vectors);
if (MATRIX(values, 2, 1) > 0) {
MATRIX(values, 2, 1) = -MATRIX(values, 2, 1);
MATRIX(values, 3, 1) = -MATRIX(values, 3, 1);
}
igraph_matrix_print(&values);
printf("---\n");
igraph_matrix_print(&vectors);
printf("---\n");
/* -------------- */
options.nev=3;
options.which[0]='L' ; options.which[1]='M';
igraph_arpack_rnsolve(cb2, /*extra=*/ &data, &options, /*storage=*/ 0,
&values, &vectors);
if (MATRIX(values, 2, 1) > 0) {
MATRIX(values, 2, 1) = -MATRIX(values, 2, 1);
}
igraph_matrix_print(&values);
printf("---\n");
igraph_matrix_print(&vectors);
printf("---\n");
/* -------------- */
options.nev=3;
options.which[0]='S' ; options.which[1]='R';
igraph_arpack_rnsolve(cb2, /*extra=*/ &data, &options, /*storage=*/ 0,
&values, &vectors);
igraph_matrix_print(&values);
printf("---\n");
igraph_matrix_print(&vectors);
printf("---\n");
/* -------------- */
options.nev=3;
options.which[0]='L' ; options.which[1]='I';
igraph_arpack_rnsolve(cb2, /*extra=*/ &data, &options, /*storage=*/ 0,
&values, &vectors);
igraph_matrix_print(&values);
printf("---\n");
igraph_matrix_print(&vectors);
printf("---\n");
/* -------------- */
igraph_matrix_destroy(&values);
igraph_matrix_destroy(&vectors);
igraph_matrix_destroy(&A);
return 0;
}
int igraph_pagerank(const igraph_t *graph, igraph_vector_t *vector,
igraph_real_t *value, const igraph_vs_t vids,
igraph_bool_t directed, igraph_real_t damping,
const igraph_vector_t *weights,
igraph_arpack_options_t *options) {
igraph_matrix_t values;
igraph_matrix_t vectors;
igraph_integer_t dirmode;
igraph_vector_t outdegree;
igraph_vector_t tmp;
long int i;
long int no_of_nodes=igraph_vcount(graph);
long int no_of_edges=igraph_ecount(graph);
options->n = igraph_vcount(graph);
options->nev = 1;
options->ncv = 3;
options->which[0]='L'; options->which[1]='M';
options->start=1; /* no random start vector */
directed = directed && igraph_is_directed(graph);
if (weights && igraph_vector_size(weights) != igraph_ecount(graph))
{
IGRAPH_ERROR("Invalid length of weights vector when calculating "
"PageRank scores", IGRAPH_EINVAL);
}
IGRAPH_MATRIX_INIT_FINALLY(&values, 0, 0);
IGRAPH_MATRIX_INIT_FINALLY(&vectors, options->n, 1);
if (directed) { dirmode=IGRAPH_IN; } else { dirmode=IGRAPH_ALL; }
IGRAPH_VECTOR_INIT_FINALLY(&outdegree, options->n);
IGRAPH_VECTOR_INIT_FINALLY(&tmp, options->n);
RNG_BEGIN();
if (!weights) {
igraph_adjlist_t adjlist;
igraph_i_pagerank_data_t data = { graph, &adjlist, damping,
&outdegree, &tmp };
IGRAPH_CHECK(igraph_degree(graph, &outdegree, igraph_vss_all(),
directed ? IGRAPH_OUT : IGRAPH_ALL, /*loops=*/ 0));
/* Avoid division by zero */
for (i=0; i<options->n; i++) {
if (VECTOR(outdegree)[i]==0) {
VECTOR(outdegree)[i]=1;
}
MATRIX(vectors, i, 0) = VECTOR(outdegree)[i];
}
IGRAPH_CHECK(igraph_adjlist_init(graph, &adjlist, dirmode));
IGRAPH_FINALLY(igraph_adjlist_destroy, &adjlist);
IGRAPH_CHECK(igraph_arpack_rnsolve(igraph_i_pagerank,
&data, options, 0, &values, &vectors));
igraph_adjlist_destroy(&adjlist);
IGRAPH_FINALLY_CLEAN(1);
} else {
igraph_adjedgelist_t adjedgelist;
igraph_i_pagerank_data2_t data = { graph, &adjedgelist, weights,
damping, &outdegree, &tmp };
IGRAPH_CHECK(igraph_adjedgelist_init(graph, &adjedgelist, dirmode));
IGRAPH_FINALLY(igraph_adjedgelist_destroy, &adjedgelist);
/* Weighted degree */
for (i=0; i<no_of_edges; i++) {
long int from=IGRAPH_FROM(graph, i);
long int to=IGRAPH_TO(graph, i);
igraph_real_t weight=VECTOR(*weights)[i];
VECTOR(outdegree)[from] += weight;
if (!directed) {
VECTOR(outdegree)[to] += weight;
}
}
/* Avoid division by zero */
for (i=0; i<options->n; i++) {
if (VECTOR(outdegree)[i]==0) {
VECTOR(outdegree)[i]=1;
}
MATRIX(vectors, i, 0) = VECTOR(outdegree)[i];
}
IGRAPH_CHECK(igraph_arpack_rnsolve(igraph_i_pagerank2,
&data, options, 0, &values, &vectors));
igraph_adjedgelist_destroy(&adjedgelist);
IGRAPH_FINALLY_CLEAN(1);
}
RNG_END();
igraph_vector_destroy(&tmp);
igraph_vector_destroy(&outdegree);
IGRAPH_FINALLY_CLEAN(2);
if (value) {
*value=MATRIX(values, 0, 0);
}
if (vector) {
long int i;
igraph_vit_t vit;
long int nodes_to_calc;
igraph_real_t sum=0;
for (i=0; i<no_of_nodes; i++) {
sum += MATRIX(vectors, i, 0);
}
IGRAPH_CHECK(igraph_vit_create(graph, vids, &vit));
IGRAPH_FINALLY(igraph_vit_destroy, &vit);
nodes_to_calc=IGRAPH_VIT_SIZE(vit);
IGRAPH_CHECK(igraph_vector_resize(vector, nodes_to_calc));
for (IGRAPH_VIT_RESET(vit), i=0; !IGRAPH_VIT_END(vit);
IGRAPH_VIT_NEXT(vit), i++) {
VECTOR(*vector)[i] = MATRIX(vectors, (long int)IGRAPH_VIT_GET(vit), 0);
VECTOR(*vector)[i] /= sum;
}
igraph_vit_destroy(&vit);
IGRAPH_FINALLY_CLEAN(1);
}
if (options->info) {
IGRAPH_WARNING("Non-zero return code from ARPACK routine!");
}
igraph_matrix_destroy(&vectors);
igraph_matrix_destroy(&values);
IGRAPH_FINALLY_CLEAN(2);
return 0;
}
