1. Computer Science and Engineering, Southern University of Science and Technology, 255310 Shenzhen, Guangdong, China, (e-mail: zhoul6@sustech.edu.cn)
2. Computer Science and Engineering, Southern University of Science and Technology, 255310 Shenzhen, Guangdong, China, 518055 (e-mail: zhangfw@sustech.edu.cn)
3. Computer Science, Boise State University, 1791 Boise, Idaho, United States, 83702 (e-mail: jidongxiao@boisestate.edu)
4. Computer Science and Engineering, University of Michigan, 1259 Ann Arbor, Michigan, United States, (e-mail: kjleach@umich.edu)
5. Computer Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, (e-mail: weimerw@umich.edu)
6. School of Information Systems, Singapore Management University, Singapore, Singapore, Singapore, 178902 (e-mail: xhding@smu.edu.sg)
7. School of Computer Science and Educational Software, Guangzhou University, 47875 Guangzhou, Guangdong, China, (e-mail: csgjwang@gzhu.edu.cn)