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Top500 list: TechWorld asks "can we believe the hype"

Article in Australian TechWorld about the Top500 as an upper bound on available compute performance.

“The Top500 list is only useful in telling you the absolute upper bound of the capabilities of the computers,” Loft says. “It’s not useful in terms of telling you their utility in real scientific calculations.”

The problem, he says, is that placement on the Top500 list is determined by performance on a decades-old benchmark called Linpack, which is Fortran code that measures the speed of processors on floating-point math operations — for example, multiplying two long decimal numbers. It’s not meant to rate the overall performance of an application, especially one that does a lot of interprocessor communication or memory access.

…It’s nice to have that processor run very fast, of course, but getting to the end of a 100-year climate simulation requires an enormous number of memory accesses by a processor, something that typically happens much more slowly. In addition, some applications require passing many messages from one processor to another, which can also be relatively slow.

It’s nice to see a fairly in-depth article in the trade press about our industry. The article goes on to talk about some of the roadblocks to good parallel performance, and highlights some future directions.

“The trend is to large numbers of [processor] cores on a single die,” he says. “And it looks like we’ll have this one chip with different kinds of cores on it. We might have cores that specialize in floating point, ones that specialize in graphics and those that are more commodity-based.” Exploiting that flexibility so the chip is, in essence, tuned for a specific application domain, such as climate modeling, will require software tools that do not yet exist, he says.

…He says Intel is also working on increasing the communication bandwidth of the individual pins that connect the processor chip to the memory controller. “I’d like to push the memory bandwidth to be 10 times greater than it is today by 2013 or 2014,” Pawlowski says. “The engineers working for me say I’m crazy, but it’s a goal.”

Overall, good piece.

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