Cray CTO Says Cray Computers Are Great

Jan Stafford writes "Linux clusters can not offer the same price-performance as supercomputers, according to Paul Terry, chief technology officer of Burnaby, British Columbia-based Cray Canada. In this interview, Terry explains that assertion and describes Cray's new Linux-based XD1 system, which will be priced competitively with other types of high-end Linux clusters."

Comments

Re:The issues are progress and long-term usefulnes

[Marx_Mrvelous]

There are some limitations to clusters that "supercomputers" don't have. Even if your network were exactly as fast as the internal bus of one of the Cray supercomputers (which I highly doubt it is), you still have a logical layer on top of it (TCP/IP/UDP etc). This slows it down.

For some applications, a cluster of slow PCs is ok. Bu if you want to do real time-intensive computation, you really can't beat a good internal bus.

Re:Maybe "APPLE" will buy another Cray!

[Thagg]

As usual, there is more to the story. Apple brought my company in on a project back in the mid 80's when they bought the Cray. While we had to sign an NDA in blood, I doubt anybody will mind me talking about it now, almost 20 years later.

Apple was trying to design a new cpu chip. It would have had vector processing capabilities not all that different from the Cray, so they bought the Cray both to do circuit simulations on the chip and as a model for their own design.

The chip was going to be a 100 MHz chip (an astonishing speed for the time) with a four-pipleline vector processing unit.

They considered (but eventually declined to) hire us to develop some kind of 3D desktop for the Mac. The idea was this would distinguish the Mac further from other computing systems, but they wouldn't be able to emulate the interface because they didn't have the horsepower.

Anyway, that's the Apple-Cray story as I understand it. I'm sure that there is a lot more to the story than I know, of course.

Thad Beier

Re:Two words:

[iPaul]

Not quite true. First off, you get much higher bandwidth between processors using proprietary (NUMA) based interconnects than you can with commodity hardware. Why? Because you can optimize for your situation. Second you can exploit things like cache-coherency between processors (even if they're in different "nodes") and therefore true shared memory. So, a 1024 processor SGI Altrix, or a 256 processor Cray is one computer as far as the OS and user-land stuff is concerned.

There's another advantage Cray has on the SV and X series and that's a vector unit on the processor. That allows you to conduct operations on arrays of numbers at once instead of having to cycle through the numbers in a loop. For example, the dot_product between two small arrays might be accomplished with one or two instructions, as opposed to a loop. Apple's AltiVec is also a vector unit.

If you took money out of the picture it would be easier to deal with a big-honkin' super computer like an SGI or Cray rather than a cluster. One computer is easier to manage and you could always use threads and plain old heap memory (which is much faster than message passing over a network).

Add money back in and 500,000 goes a lot farther in raw compute power when you're buying racks of DELLs and infiniband interconnects. However, depending on the application, you may be faster, slower, or even dog-slow compared to the cray. If you need the answer today, and the $ is not a factor, go to Cray or SGI with a blank check. If you have to balance cost and time, then a cluster might be better.

Essentially, it boils down to how much communication you do between nodes. Cray does it orders of magnitude faster than off-the-shelf stuff. If you hardly ever pass messages between nodes, clusters are fast. If you have to pass a lot of messages between nodes, one big computer will trounce lots of little ones.