1. Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zürich, Switzerland
2. LERMA, Observatoire de Paris, PSL Research Univ., CNRS, Sorbonne Univ., UPMC Univ. Paris 06, F-75014 Paris, France
3. Systems Group, ETH Zurich, Universitätstrasse 6, CH-8006 Zürich, Switzerland
4. Eureka Scientific, 2452 Delmer Street Suite 100, Oakland, CA 94602-3017, USA
5. Institute of Network Computing and Information Systems, Peking University, Yiheyuan Lu, Haidian District, Beijing 100871, China