Newer supercomputers favor energy efficiency over raw speed, Top500 rankings suggest

There's no change at the top, with China's 33.86 petaflop/s Tianhe-2 in the lead for the sixth consecutive time.

In fact, there are only two changes to the top 10. Trinity, built by Cray for the U.S. Department of Energy's Los Alamos and Sandia national laboratories, jumped straight in at sixth place, while another Cray machine climbed up the rankings to eighth place. Hazel-Hen, at Germany's Höchstleistungsrechenzentrum Stuttgart (HLRS), now has double the number of cores it had six months ago, when it was known as Hornet and held 23rd place.

The Top500 list, now in its 46th edition, is published twice yearly by supercomputing experts in the U.S. and Germany.

In recent years the list's compilers have noted that the pace of supercomputer growth is slowing compared to the long-term trend, and this year, they say, is no exception.

The most significant changes, though, come when the world's 500 fastest supercomputers are ranked by energy efficiency, measured in flops/watt.

The leader in the efficiency stakes at 4.86 gigaflops/watt is the two-year-old Tsubame-KFC/DL, built by NEC for the Tokyo Institute of Technology, but the next six are new entrants, all from China.

In second place is a Cluster W780I built by Sugon for the Chinese Academy of Sciences' Institute of Modern Physics, delivering 4.78 Gflops/W.

It's followed by five machines using TS10000 HPC Servers from Inspur, sited at unnamed IT companies and Internet service providers.

The seven most efficient machines are all built using a mix of Intel Xeon E5 and Nvidia Tesla processors. None score particularly highly for raw speed: they are ranked 392nd, 318th, 456th, and 225th through 228th in absolute performance, respectively, but they all deliver more than 3.77 Gflops/W.

Only about half the machines on the Top500 list are rated for energy efficiency. The average was 1.45 Gflops/W this time around, compared to 1.35 Gflops/W in July.

China's presence at the top of the energy efficiency rankings is indicative of wider geographical changes in the list.

The number of U.S. systems in the top 500 has dropped to 201, from 231 in July, while the European share has dropped from 141 to 107. China has now overtaken Europe, with 109 machines on the list, up from 37 in July.