Li Yang
School of Computer Science, Southwest Petroleum University, Chengdu 610500, Sichuan, China; College of Computer, Sichuan University, Chengdu 610065, Sichuan, China
Xinyu Gen
School of Computer Science, Southwest Petroleum University, Chengdu 610500, Sichuan, China; College of Computer, Sichuan University, Chengdu 610065, Sichuan, China
Xiedong Cao
College of Computer, Sichuan University, Chengdu 610065, Sichuan, China
Jun Zhang
Department of Computer Science, University of Kentucky, Lexington 40506-0633, USA