Department of Computer Science and Engineering, University of Washington, Seattle, WA 98105, USA. jcarlson@cs.washington.edu|Department of Computer Science and Engineering, University of Washington, Seattle, WA 98105, USA. jcarlson@cs.washington.edu|Department of Computer Science and Engineering, University of Washington, Seattle, WA 98105, USA. jcarlson@cs.washington.edu|Department of Computer Science and Engineering, University of Washington, Seattle, WA 98105, USA. jcarlson@cs.washington.edu