1. School of Computing, University of Kent,
Canterbury CT2 7NF, United Kingdom
2. Brain-like Computing Center, Tsinghua University, Beijing 100084, China
3. Institute of Micro-Electronics/Beijing Innovation Center for Future Chips, Tsinghua University, Beijing 100084,
China
4. Department of Electrical Engineering and Computer Science, University of California, Berkeley, California 94720-1770,
USA