1. College of Computer and Information Science, Southwest University, Chongqing, China
2. Chongqing Institute of Green and Intelligent Technology, Chongqing Engineering Research Center of Big Data Application for Smart Cities and the Chongqing Key Laboratory of Big Data and Intelligent Computing, Chinese Academy of Sciences, Chongqing, China
3. Department of Computer Science, Brunel University London, Uxbridge, U.K.