1. MIT Sloan School of Management, Cambridge, Massachusetts 02142;
2. Laboratory for Financial Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142;
3. Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02142;
4. Santa Fe Institute, Santa Fe, New Mexico 87501;
5. School of Mathematical Sciences, Peking University, Beijing 100871, China;
6. Laboratory for Mathematical Economics and Quantitative Finance, Peking University, Beijing 100871, China;
7. Center for Statistical Science, Peking University, Beijing 100871, China;
8. National Engineering Laboratory for Big Data Analysis and Applications, Peking University, Beijing 100871, China