Acknowledgement. The on-going research is supported by the National Science Foundation (Contract No. CCF-2114319, CNS-1909099). The past support came from the National Science Foundation (Contract No. CCF-1717877, CCF-1629376, CNS-1319617, CCF-1116104, CCF-0963759, CNS-0834566, CNS-0720796, CNS-0509270, CCR-0238176, CCR-0219848 and EIA-0080124), IBM CAS Faculty Fellowships, the Department of Energy (Contract No. DE-FG02-02ER25525), the National Science Foundation of China (Contract No. 61328201), two grants from Microsoft Research, a grant from Huawei, and equipment support from Intel. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the funding organizations.