[Wu, Chenwang;Zhou, Nan;Xu, Peilan] Univ Sci & Technol China, Sch Comp Sci & Technol, Hefei 230027, Anhui, Peoples R China.^[Luo, Wenjian] Harbin Inst Technol, Sch Comp Sci & Technol, Shenzhen 518000, Guangdong, Peoples R China.^[Zhu, Tao] Univ South China, Sch Software Engn, Hengyang 421001, Hunan, Peoples R China.