1. MIT Laboratory for Financial Engineering, Cambridge, MA, USA; MIT Sloan School of Management, Cambridge, MA, USA; MIT Computer Science and Artificial Intelligence Laboratory, Cambridge, MA, USA; Santa Fe Institute, Santa Fe, NM, USA
2. School of Mathematical Sciences, Peking University, Beijing, China; Center for Statistical Science, Peking University, Beijing, China; National Engineering Laboratory for Big Data Analysis and Applications, Peking University, Beijing, China