College of Computer Science and Technology, Jilin Univesity, 2699 Qianjin St, Changchun, China.|College of Computer Science and Technology, Jilin Univesity, 2699 Qianjin St, Changchun, China.|College of Computer Science and Technology, Jilin Univesity, 2699 Qianjin St, Changchun, China.|College of Computer Science and Technology, Jilin Univesity, 2699 Qianjin St, Changchun, China.|Department of Computer Science, Rutgers, The State University of New Jersey, 2699 Qianjin St, Piscataway, NJ, USA.|College of Computer Science and Technology, Jilin Univesity, 2699 Qianjin St, Changchun, China. huanglan@jlu.edu.cn.