1. Department of Computer Science and Engineering, Chongqing University, Chongqing, 400044, P. R. China
2. Department of Computer Science, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
3. Parallelism, Algorithms and Architectures Research Centre, Department of Computer Science, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK