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Have you looked at the Knights Landing architecture? It seems that the 3d stacked memory design would greatly accelerate such an application.
by maaku 11y ago
Have you looked at the Knights Landing architecture? It seems that the 3d stacked memory design would greatly accelerate such an application.
- tromp 11y agoYes; I tried a Xeon Phi. And I reported my experience as: I wanted to treat the Xeon Phi like a regular Xeon with just many more cores. So I ran my benchmark mostly unchanged. I was surprised however that the single threaded performance was roughly 20x lower than a normal Xeon. Using all 240 threads I was still doing no better than with 12 cores on a normal Xeon. It seems that the Xeon Phi memory subsystem is not really optimized for multithreaded random access. The provider of that system suggested that I ought to perform computation and memory access (including prefetching) on the SIMD units (VPUs), but I haven't gotten around to studying the use of VPUs yet...
- trsohmers 11y agoThe Knights Corner (2012-2015) Xeon Phi was based on a modified and scaled down version of the Intel P54C core... the same one used in the original 1995 Pentium. On top of that, each core only runs at 1.053 to 1.1GHz. Why would you think that single threaded performance would be any good for an in order superscalar core that is 20 years old?
- rbanffy 11y agoIIRC, it's actually a bit worse: each core could run two threads, but they'd run alternating clock cycles, like the Cell PPUs - unless you have two threads running, each core has half that speed. A normal optimization trick of spreading across as many cores as possible backfires here. But that was integer performance. Each core also had a beefy SIMD unit, twice as wide as the one in then current Xeons.
- maaku 11y agoI was specifically asking about Knights Landing because it has an entirely different memory subsystem than Xeon Phi. You might want to take a look at that.