[1] Sch. of Comp. Sci. and Engineering, University of New South Wales, Sydney, NSW 2052, Australia
[2] Dept. of Comp. Sci. and Technology, Tsinghua University, Beijing, 100084, China
[3] Vis. Info. Processing Laboratory, Sch. of Comp. Sci. and Engineering, University of New South Wales, Sydney, NSW, Australia
[4] Computer Science Department, University of Massachusetts, Amherst, MA, United States
[5] Purdue University, West Lafayette, IN, United States
[6] Beckman Institute, University of Illinois, Urbana-Chamgain, IL, United States