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by spydum 4194 days ago
doing very little times 2300 in parallel is sort of the point though. if you have a parallel optimized job (like sum/agg of many rows/table), it is stupid difficult to make fast on a complex CPU where most of the execution paths remain unused. you must wait for the instruction pipeline to clear, and you can only process so many ops per cycle (whats a popular core count now on a big cpu system? 48-96 threads i think my UCS blades can run). when you are talking THOUSANDS of cores on a weee baby 250w GPU card, of which I can put TWO OF in each system? That is enormously powerful for those parallel tasks.
1 comments
vardump 4193 days ago
In that case my 4 core is really -- waves hands -- a 576 core system. 4 cores, maybe 2 AVX 8-wide instructions execute 2 * 8 * 4 and maybe 3 stages are in flight. And 3x the clock. Or something. So I'm getting roughly comparable completely meaningless 2 * 8 * 4 * 3 * 3 cores.

I'm not suggesting CPU resources should be counted like that, but that's closer to have GPU resources are counted. Sure, it sounds impressive, but does that 2304 cores really represent fair truth to, say, 4 CPU cores?

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msandford 4193 days ago
While we're making hand-wavey comparisons, I'll make one.

NVidia GPUs have a theoretical peak of about 3-5 TFlops for 250 watts. http://en.wikipedia.org/wiki/List_of_Nvidia_graphics_process...

Xeons have a theoretical peak of about 0.5-1 TFlops for 150 watts. http://www.microway.com/hpc-tech-tips/intel-xeon-e5-2600-v3-...

Is that completely apples-to-apples? Probably not since the Xeon is probably talking about double precision floating point versus single precision on the GPU. But for a lot of database applications which don't involve money, single precision floats have a sufficient level of accuracy for the performance improvement to be attractive.

Yeah the performance isn't 100x like it used to be but it's still enough that if you have racks and racks full of machines a 3-10x improvement could be really substantial. Going from $10k/mo in rent to $1k/mo in rent at a datacenter could make or break an early stage startup.

Further as things get cheaper they get used a lot more. Scientists have only two models: the ones they can run but don't really like and the ones they want to run. Adding fidelity to modeling codes isn't an absolute good but it's hard to argue that it makes the world worse.

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