Project Appleseed Updated

J. FoxGlov writes "UCLA's Project Appleseed has been updated with new benchmarks showing their clusters of Macintosh G3s and G4s running neck and neck with Crays and kicking the snot out of Pentium II clusters, generating fractal clusters in parallel. Includes the recipe for making your own Apple-flavored Beowulf cluster. "

Comments

Don't believe all the hype.

[Richard Mills]

Don't believe all this hype and go sell your Crays just yet. What many people fail to realize is that the total number of achievable MFLOPS of all the nodes in a parallel machine IS NOT a very meaningful measure of how powerful or useful the machine is. This ignores the nature of the interconnect between the processors, memory, etc., which is *extremely* important in most parallel computations, and is what makes supercomputers so damned expensive. This stuff is not Ethernet! For many types of parallel applications, Ethernet becomes such a bottleneck that no advantages can be realized from parallelizing an application.

The generation of fractal clusters is a classic example of what are known as "embarassingly parallel" problems in parallel computing circles. As you iterate points in the set, their evolution is independent, so a minimum of message passing is required. (In computer science-ese, "the computational graph is disconnected"). With even the crummiest of interconnects, you can get good results out of parallelizing these fractal cluster generators because the only thing that will really make a difference is the total number of FLOPS acheivable by each of the nodes. Fractal set generation is just not a very meaningful benchmark.

But consider, say, a finite-element model where every point in your grid is affected by its neighbors. Then you need to do lots of message passing, and the nature of the interconnect becomes orders of magnitude more important. In this case, I guarantee you that a commercial supercomputer is going to beat the pants off of any cluster machine. This is not to say that cluster machines aren't useful, but a real "supercomputer" still has its place.

I took the undergraduate course...

[levl289]

I attended ucla as a physics major while this project was still under way, and took a more basic, introduction to computer modelling of plasma systems. The professor doing a lot of the work in this field is John Dawson. Along with him, and IIRC, more in charge of the computer systems, is Victor Decyk.
Decyck taught half of the class, although he was technically a TA. He explained the progression away from high $$ "super computers", such as Crays, and the usefulness of clusters.

I also had the honor of working at JPL, where Decyk was a part-time scientist in the computing/analysis department for the Experimental Measurment Devices group.
If you look up something like "computer plasma modelling" on the 'net, you'll very likely find papers by these two...very interesting high-powered stuff - the mind boggles at just how much the computer is crunching when you realize that a large number of the plasma particles are interrelated spatially.