int nV =
30000;
int num =
0;
Graph G(nV);
synchronize(G);
std::vector<int> localComponent(nV);
LocalMap components(localComponent.begin(),get(vertex_index, G));
add_edge(vertex(0,G),vertex(1,G),G);
add_edge(vertex(29998,G),vertex(29999,G),G);
num = connected_components_ps(G, components);