void run_fiber() {
   while (1) {
     size_t lvid = ctr.inc_ret_last();
     if (lvid >= graph.num_local_vertices() || !vset.l_contains(lvid)) break;
     typename GraphType::local_vertex_type l_vertex = graph.l_vertex(lvid);
     if (l_vertex.owned()) {
       typename GraphType::vertex_type vertex(l_vertex);
       INCREMENT_EVENT(EVENT_WARP_PARFOR_VERTEX_COUNT, 1);
       fn(vertex);
     }
   } 
 }