1. Center for Energy-Efficient Computing and Applications, Peking University, Beijing, China
2. Computer Science Department, University of California, Los Angeles, USA
3. Center for Energy-Efficient Computing and Applications, Peking University, Beijing, China and PKU/UCLA Joint Research Institute in Science and Engineering
4. Center for Energy-Efficient Computing and Applications, Peking University, Beijing, China and Computer Science Department, University of California, Los Angeles, USA and PKU/UCLA Joint Research Institute in Science and Engineering