[1] Department of Computer Science and Engineering, University of California at San Diego, San Diego, CA, United States
[2] Faculty of Mathematics, NASA Ames Research Center, University of Bucharest, United States
[3] Department of Computer Science and Engineering, University of California at San Diego, San Diego, CA 92093-0114, United States
[4] Department of Computer Science, University of Illinois, Urbana-Champaign, IL, United States