[Wu, Libing;Dang, Ping;Nei, Lei;Liu, Bingyi] Wuhan Univ, Sch Comp Sci, Wuhan 430072, Peoples R China.^[Wu, Libing;Nei, Lei] Wuhan Univ, State Key Lab Software Engn, Wuhan 430072, Peoples R China.^[Cui, Jianqun] Cent China Normal Univ, Sch Comp Sci, Wuhan, Peoples R China.