http://brucerain.github.io/2014/10/02/%E9%80%89%E6%8B%A9%E5%90%88%E9%80%82%E7%9A%84%E6%8E%A8%E8%8D%90%E6%A8%A1%E5%9E%8B/
http://cloga.info/graphlab%20create/2014/07/26/graphlab_create/