1. David R. Cheriton School of Computer Science, University of Waterloo, Waterloo, Ontario, Canada.
2. Inria Grenoble, Rhône-Alpes, France.
3. Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada.
4. Department of Combinatorics and Optimization, University of Waterloo, Waterloo, Ontario, Canada.
5. Department of Biology, York University, Toronto, Ontario, Canada.