These lecture notes are copyrighted material. Use of these pages for the class CMSC818Z at the University of Maryland is permitted. The lecture notes sometimes contain figures from the class textbook, High Performance Computing, which is coprighted by Andrew Tanenbaum. Personal use of these notes by individuals at other locations is also permitted. Any other use requires permission of the author (Jeffrey K. Hollingsworth, hollings@cs.umd.edu)