June 2013 Top500 List Published: Xeon Phi Takes Top Spot

Kicking off this week is the International Supercomputing Conference in Leipzig, Germany, one of the two major supercomputing/high performance computing conferences of the year. There will be several announcements coming out of ISC this week – a few of which we’ll see later this week – but perhaps the most visible announcement that comes out of ISC is the annual summer refresh of the Top500 supercomputer list.

With that in mind, the June 2013 Top500 list has been released, and as is usually the case a new supercomputer has entered the fray at the top of the list. The latest addition and new #1 supercomputer is the Chinese National University of Defense Technology's Tianhe-2 supercomputer, which hits the list with a measured Linpack performance of 33.86PFLOPS, nearly double the previous #1, Oak Ridge National Laboratory’s Titan. Like Titan, Tianhe-2 is another hybrid system, using a custom interconnect to tie together numerous systems containing both traditional Intel Xeon CPUs and Intel’s Xeon Phi co-processors.

Tianhe-2 is not the first Xeon Phi system in the list, but this marks the first time that a Xeon Phi system has taken the top spot. Next to the AMD Opteron plus NVIDIA Tesla based Titan, the #1 spot in recent editions of the list has also been held by IBM BlueGene/Q systems, and SPARC64 based systems, making Tianhe-2 the 4^th architecture in 2 years to take the top spot. Tianhe-2 means that Xeon Phi now occupies two of the top 10 positions, with the previously launched Stampede system moving up the list from #7 to #6.

Looking at the latest data, what’s particularly astounding about Tianhe-2 is simply how large it is. Placing on the Top500 list requires both efficiency and brute force, and in the case of Tianhe-2 there’s an unprecedented amount of brute force in play. The official power consumption rating for Tianhe-2 is 17.8 megawatts, more than double Titan’s 8.2MW. Even going back several years, the second largest machine to hit the Top500 list – and thus far the only other machine over 10MW – is the K supercomputer, at 12.6MW. Simply put, from a power perspective Tianhe-2 is nearly 50% larger than any previous Top500 computer.

When it comes to efficiency the matter won’t technically be settled until the formal unveiling of the Green500 list later this week, but since it’s just a derivation of the Top500 it’s fairly easy to calculate. To that end while Tianhe-2 isn’t quite as efficient as the BlueGene/Q and Tesla systems that sit in the top 5, both of which are just over 2,100 MFLOPS/watt, at 1901 MFLOPS/watt Tianhe-2 is at least in the same general category and generation as these other systems. With all of these supercomputers interconnects play a big part in performance, so for a system as large as Tianhe-2 that’s especially true. Unfortunately very few details have been published about the custom interconnect Tianhe-2 uses, so there’s very little to say on the matte other than that whatever it is works well enough to scale well over Tianhe-2’s 16,000 nodes.

Wrapping things up, with the introduction of Tianhe-2 this marks the second hybrid system in as many editions of the list to take the top spot. Although hybrid systems have been in the Top500 for a few years now, they have continued to become more popular due to the high efficiency and density of GPUs and GPU-like processors. Though straight CPU systems such as BlueGene/Q and its ilk are by no means out of the running, it will be interesting to see if this is part of a larger trend. According to the Top500 list the number of hybrid systems is actually down – from 62 on the last list to 54 now – but on the other hand the continued improvement and increasing flexibility of GPUs and other co-processors, not to mention the fact that now even Intel is involved in this field, means that there’s more effort than ever going into developing these hybrid systems. So whether hybrids will continue to push out straight CPU systems at the top of the list will be an interesting thing to keep an eye on over the next couple of years.