Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota. njohnson@cs.umn.edu.|Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota. huanan@cs.umn.edu.|Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota. gang.fang@mssm.edu.|Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota. kumar@cs.umn.edu.|Department of Computer Science and Engineering, University of Minnesota, Minneapolis, Minnesota. kuang@cs.umn.edu.