Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA. sroy@broadinstitute.org|Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA. sroy@broadinstitute.org|Department of Computer Science, University of New Mexico, Albuquerque, NM 87131, USA. sroy@broadinstitute.org