Parallel computing is a simple concept: Take a big task, split it into a set of smaller tasks, and give each task to a separate computer. But, making it work in a scalable, reliable manner is difficult.
As the number of processors increases, the latency of the communication between processors becomes a limiting factor. In fact, scheduling scarce communications resources for even just a 64-processor machine is like choreographing a performance of ballet dancers and machine-gunners. If everything works just right, one sees an awesome display of numerical grace and firepower. If something goes wrong, though, things get so bad so fast that it takes two weeks just to figure out what happened in that fatal split-second. Debugging parallel programs on machines which are generating over a billion wrong numbers per second is a considerable challenge and a sure-fire way to blow a weekend.
Full text of my thesis "Tasks and Connection Sets: Choreographed Communication on a Connection-based Parallel Computer" is available in Adobe Acrobat format or Postscript format.
Some of my favorite photos to date
Noll, D.; Webb, J.; Warfel, T.; "Parallel Data Resampling and Fourier
Inversion by the Scan-line Method", IEEE Transactions on Medical Imaging,
vol. 14, num. 3, Sept 1995, pp. 454-463.
Webb, Jon A.; Warfel, Thomas E.; Kang, Sing-Bing; A Scalable Video-Rate
Camera Interface; CMU School of Computer Science Technical Report
CMU-CS-94-192; Carnegie Mellon University; 1994.
Noll, D.; Warfel, T.; "Parallel MRI Deblurring", poster session at
Supercomputing 93.
Feldmann, A.; Stricker, T.M.; Warfel, T.E.;"Supporting sets of arbitrary
connections on iWarp through communication context switches,"
Proceedings of the 5th Annual ACM Symposium on Parallel Algorithms and
Architectures; pp. 203-212; 1993.
Warfel, T.E.; Noll, D.C.; "Parallel Deblurring for Non-spin-warp Imaging";
Soc. of Magnetic Resonance in Medicine, 11th Ann. Mtg.; p. 473,
August 1992. (conference abstract, presentation)
Mintun, M.A.; Warfel, T.E.; Schuster, D.P.; "Evaluating pulmonary vascular
permeability with radiolabeled proteins: an error analysis"; Journal of
Applied Physiology, vol. 68, pp. 1696-1706; April 1990.
John December at RPI has a nifty Summary of Internet tools.
Tom Warfel,
warfelte@msx.upmc.edu / tew+@cs.cmu.edu