Slashdot Mirror

SteveBoker writes "Tomorrow and Friday is a conference on Learning and Multimodal Communication. This conference looks at how cognitive psychology can inform the use of technology in the classroom. The conference is unusual in that it both addresses the topic of telepresence technology and uses The Access Grid to present the conference. The speakers will be at four sites: University of Chicago, University of Illinois Urbana Champaign, University of Illinois Chicago, and University of California San Diego. The conference will be webcast in Quicktime here(1), here(2), here(3) , and here(4) (no registration required). Full Disclosure: I am presenting a talk on modeling interpersonal coordination using motion capture of dancers in order to design convincing telepresence avatars."

Short Circuit writes "Secunia has issued a security advisory for Mozilla and Firefox. Apparently, remote web sites can spoof the user interface using XUL. (See the Firefox proof of concept.) Of course, that won't stop me from using Firefox."

Daerk writes "ECCp-109 has been solved. A week ago. Now wonder my stats haven't updated. Now what am I going to do till climateprediction.net goes live..."

b0r0din writes: "CNN has this article about a way to force computers to solve complex computational problem using the checksum algorithm used by the TCP/IP protocol. For more technical details, see their website." You probably thought learning TCP/IP was useless. No! You can use it to make an extremely inefficient computer...

Nothing I like better than post X-Files quickies. Oh wait. That came out wrong. (rimshot) I should post some links quick to cover up my terrible joke: Eduardo Silva sent us a link to the online version of At RMSs Essay from Open Sources. It's on the past, present and future of the FSF. Jaws sent us a link to a Katz article at Mercury Center called The End of the Microsoft Age. Dan Guisinger sent us a link to some new Rio Accessories including a remote control that plugs into the headphone jack. Andy King sent us a link to the Web Reference entry for the Slashdot Effect Elphin sent us a link to a nifty poster of the Netscape color palette. GtHS sent us a link to an article that the trillions of you who continue to submit the hamster dance will like: It's the Penguin Dance. Pete Rijks sent us a link to the Scary Squirrels for all you conspiracy nuts. GTM writes The Net Wars Trilogy, a strange net parody of a certain trilogy you might like. baegucb sent us a link to another site on the hot topic of furby mutiliation. This time with a microwave. jchildress@netspeak.com sent us a link to another scary patent. How does this stuff get in the system?

Michael Eilers has written a sort of introduction to Beowulf, what it does, what it doesn't do, and why we should care. It really is a sort of quickie distributed computing FAQ that many of you might enjoy. So hit the link below and find out. The following is a feature by Slashdot Reader Michael Eilers Beowulf beyond the Hype A Quickstart to the Beowulf Concept During the last weeks the Beowulf project got a lot of attention in the PC press and even on Slashdot. With Red Hat's Extreme Linux CD the relevant mailing lists show an increasing number of newbie questions. Unfortunately the informat ion Red Hat provides on their Extreme Linux web pages is less than informative and full of hype. This may result in disappointed users. It seems appropriate to make some comments an hardware and software and give some guidance for the v ery beginner.

The name Beowulf stems from an old English tale and was the name of the first e xample of this class of computers. In fact a Beowulf is nothing else as a local computer network. You might say I have a small network in my flat (f.e. an old 486 connected to my newer machine), do I have a Beowulf? The answer is yes. Yo u do own already the hardware to start. Even if your connection is via PLIP/SLI P you can call your construction a Beowulf as soon as ping is successf ul. Forget all the hype about expensive special networking stuff like switches, Myrinet or SCI. For some tasks it is helpful but others won't benefit. A 10/10 0Mb connection seems to be sufficient for serious starting.

A Beowulf is not a solution for all of your speed problems. Building a Beowulf has not the same effect as f.e. the increasing of clock speed. With a Beowulf y ou won't see a speedup of your daily software and the class of software that is already adopted to Beowulfs can have very different speedups.

The hardware part is nothing more than connecting PCs with standard networking hardware. The main idea is to make your PCs to talk to each other. The most com mon solution is message passing. There are two main ways for doing message pass ing: PVM and MPI. The decision between them is mainly a matter of taste (see here for a comparing paper). I will foc us on PVM but keep in mind that MPI is as good. You can get that stuff here. The pvm3.x.x.tar.gz package has a long history and is rock solid stuff. Sinc e 1993 I did install it on half a dozen unices and never met a major problem. A fter unpacking and compiling play around (yes there is a "hello world" example) . After playing with the examples. You will see that the main commands are pvm_ send and pvm_receive and If you think that you do understand the examples start your own programming If you know what matrix multiplication is, try to impleme nt a parallel version. This is an instructive example. If you have problems you may ask for a debugging utility. Try to get xpvm-1.2.5.tar.gz from the above U RL. Its not a debugger but it visualises the behaviour of your parallel code. T he whole thing may take you two or three evenings. After that you know the basi cs of the Beowulf concept of making a pile of PCs looking as one machine.

Now you may have some questions:

Q: Sounds interesting, but I don't have a network at home. What can I do?
A: You have a network (the loopback device) in your Linux box. This means that you can install PVM/MPI and play with it. Of course you won't see a speedup. :-(

Q: I have access to a computer pool but I'm only a common user.
A: You don't have to be "root". You can install PVM/MPI as a normal user and tr ansform this pool in your personal Beowulf.

Q: I'm not a C programmer, but I use [Perl|Tcl|Python]?
A: There are interfaces available at the PVM home page (MPI??).

Q: Im not a programmer. Are there interesting applications?
A: Im sure there are plenty of applications that exploit the power of Beowulfs. Most of the stuff lives in academic environment and this means that availabilit y and quality differs. I use f.e. GAMESS a quantum chemistry program that uses MPI. Maybe one appl ication need's to be specially mentioned. There are two Beowulf-ready patches f or the famous POVray ray-tracing program. PV MPOV is more flexible but less robust and FLY3 is robust but a little inflexible. If you use POVray very o ften and play with the idea of buying a PII[34]00 MHz you may rethink this idea if you checked the povbench res ults at The fastest rendering was done with a messa ge passing version of povray.

Q: If you state that building and using of Beowulfs is that easy why aren't the re more Beowulfs?
A: I don't know why there aren't more, but I think this situation will change.

Q: I'm a little confused about the many packages that allows computing of Beowu lfs?
A: Indeed there is a whole zoo of packages for programming networked workstatio ns. For a first attempt you don't need them but some of them solve special prob lems. For an overview about the important ones check out the "Linux Parallel Pr ocessing HOWTO" by Hank Dietz.

Q: Is there a PVM/MPI version for Windows95?
A: Yes there are Win32 versions of PVM and MPI, but who cares. In fact every (pseudo)multitasking operating system with network support can in principal be used to build a Beowulf (f.e. there is Win 3.x port for PVM).

Q: Where can I get more Information?
A: As you may have seen from the above the message passing part is the stuff th at is tricky. You find links to books and tutorial for parallel programming on the PVM/MPI home pages. Hardware related information at introductory level you will find in the "Beowulf HOWTO" by Jacek Radajewski and Doug Eadline. A comprehensive overv iew on hardware and software in the "Linux Parallel Programming HOWTO" by Hank Dietz.

Q: Do I need the Beowulf software packages from the Beowulf project at NASA?
A: If you use Linux, then you probably use one of the network driver developed by Donald Becker. So the Beowulf project is already at your home and in this se nse necessary. The rest of NASA's Beowulf software provided for the use with cl usters helps you to manage a large cluster but it's not necessary and probably not the first step to do and beyond the scope of a quickstart. Even the suits a t NASA have realized that Beowulfs are a powerful tool, but the shutdown of the Beowulf web pages is like preventing the production of cars by closing a horn factory.

Q: If you can connect local PC's to look as one computer, why not coupling comp uters via Internet to a supercomputer?
A: Standard message passing software uses communication protocols that are very sensitive to packet loss. But there are activities in this area. Look for the keywords "metacomputing" or "hypercomputing".

Michael Eilers