Today's plan

Grid Computing

a few problems, many from grid.org:
- Search for Extra-Terrestrial Intelligence (SETI@Home), analyzing radio signals for patterns
- research into cancer, anthrax, smallpox: screening good candidate drugs that might "fit" (and therefore fight) disease proteins
- humane proteome folding: using genome information to compute protein folding to figure out protein function
e.g. the cancer research project
- "allows your computer to screen molecules that may be developed into drugs to fight cancer. Each individual computer analyzes a few molecules and then sends the results back over the Internet for further research."
- "download a very small, no cost, non-invasive software program that works like a screensaver: it runs when your computer isn't being used"
- "There is no cost to participate and no impact on your computer use. The project software cannot detect or transfer anything on your machine but project-specific information."
also the World Community Grid

massively parallel problems, only works when there is much computation per unit of communication (problem can be partitioned, e.g. search for molecules or encryption keys)
good PR is needed to enroll volunteers -- need prizes ("points"), perhaps publicity (lottery-like system)
individual processors will become unavailable -- need strategies to deal with that, e.g. replicate processing
cannot trust that malicious individuals (e.g. your competitors) won't try to contaminate your results:
- could replicate processing on unrelated computers
- could double-check (on a trusted computer) results that are "too good to be true"
not a conventional operating system, but does need OS-like support for replicated computation, process migration,

Multiple computers used to solve a single problem are a cluster
clustering can be used for high availability, e.g. replicated servers
clustering can also be used for high performance http://www.beowulf.org/overview/index.html:
Beowulf Clusters are scalable performance clusters based on commodity hardware, on a private system network, with open source software (Linux) infrastructure. The designer can improve performance proportionally with added machines.
Common uses are traditional technical applications such as simulations, biotechnology, and petro-clusters [petroleum visualization]; financial market modeling, data mining and stream processing; and Internet servers for audio and games.

commodity hardware, often x86 based, usually homogeneous (all machines have similar capabilities)
programming model is independent of the specifics of the underlying hardware (commodity processors, commodity networks), even though specific network design (device driver) may be customized for higher performance
programming model based on standard libraries such as MPI (Message Passing Interface) and PVM (Parallel Virtual Machine), as well as free OS and programming tools
each processor runs linux, and standard protocols are used for communication
PVM supports the distribution of work, where a single multiprocessing program executes transparently on any available processors

clusters are not new, but
have often been one-of-a-kind or proprietary
beowulf allows the creation of inexpensive, custom supercomputers
based on the realization that off-the shelf (COTS) hardware and software could be combined into a supercomputer