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#include <igraph.h>
int main(void) {
igraph_t graph;
igraph_vector_int_t dimvector;
igraph_vector_int_t edges;
igraph_vector_bool_t periodic;
igraph_real_t avg_path_len;
igraph_vector_int_init(&dimvector, 2);
VECTOR(dimvector)[0]=30;
VECTOR(dimvector)[1]=30;
igraph_vector_bool_init(&periodic, 2);
igraph_vector_bool_fill(&periodic, true);
igraph_square_lattice(&graph, &dimvector, 0, IGRAPH_UNDIRECTED, /* mutual= */ false, &periodic);
igraph_average_path_length(&graph, &avg_path_len, NULL, IGRAPH_UNDIRECTED, /* unconn= */ true);
printf("Average path length (lattice): %g\n", (double) avg_path_len);
igraph_rng_seed(igraph_rng_default(), 42); /* seed RNG before first use */
igraph_vector_int_init(&edges, 20);
for (igraph_integer_t i=0; i < igraph_vector_int_size(&edges); i++) {
VECTOR(edges)[i] = RNG_INTEGER(0, igraph_vcount(&graph) - 1);
}
igraph_add_edges(&graph, &edges, NULL);
igraph_average_path_length(&graph, &avg_path_len, NULL, IGRAPH_UNDIRECTED, /* unconn= */ true);
printf("Average path length (randomized lattice): %g\n", (double) avg_path_len);
igraph_vector_bool_destroy(&periodic);
igraph_vector_int_destroy(&dimvector);
igraph_vector_int_destroy(&edges);
igraph_destroy(&graph);
return 0;
}
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