1. Zhongguancun Laboratory, Beijing, China
2. Department of Computer Science, City University of Hong Kong, Hong Kong SAR, China
3. Microsoft Research Asia, Beijing, China
4. Shandong Provincial Key Laboratory of Computer Networks, Shandong Computer Science Center (National Supercomputer Center in Jinan), Qilu University of Technology (Shandong Academy of Sciences), China
5. Department of Computer Science and Engineering, The Chinese University of Hong Kong, Hong Kong SAR, China