[1] Shanghai Univ, Sch Comp Engn & Sci, Shanghai, Peoples R China
[2] City Univ Hong Kong, Dept Comp Sci, Hong Kong, Hong Kong, Peoples R China
[3] Shanghai Univ, Sch Comp Engn & Sci, Shanghai 200072, Peoples R China
[4] Beijing Normal Univ, Beijing 100875, Peoples R China