1. School of Computer Science and Technology, Heilongjiang University, Harbin, China
2. Department of Computer Science and Technology, Tsinghua University, Beijing, China
3. School of Mathematical Science, Heilongjiang University, Harbin, China
4. College of Math and Computer Science, Institute for Systems Biology, Jianghan University, Wuhan, China
5. Department of Computer Science and Engineering, Washington University in St. Louis, Saint Louis, Missouri, USA