Japan’s research institution RIKEN once again captured the top spot on the Green500 list with its Shoubu supercomputer, the most energy-efficient system in the world. With rating of 6673.84 MFLOPS/Watt, Shoubu edged out another RIKEN system, Satsuki, the number 2 system that delivered 6195.22 MFLOPS/Watt. Both are “ZettaScaler”supercomputers, employing Intel Xeon processors and PEZY-SCnp manycore accelerators.
 
The 3rd most energy-efficient system is China’s Sunway TaihuLight, which currently holds the number 1 spot on the TOP500 list as the world’s fastest supercomputer. It is powered solely by Sunway’s SW26010 processors and represents the first homogenous supercomputer in the top 10 of the Green500 since a set of IBM Blue Gene/Q systems occupied six of the top 10 spots in June 2013.
 
The Satsuki and TaihuLight supercomputers are the only new entries in the top 10. Overall, there are 157 new systems in the June 2016 edition of the Green500, representing nearly a third of the list.
 
Aside from those systems mentioned, the remaining seven supercomputers in the top 10 use GPUs as accelerators paired with Xeon CPUs. The most energy-efficient systems continue to be dominated by heterogeneous systems like these. In the current list, 40 of the top 50 systems employ some sort of accelerator.
 
GPUs are the most common accelerators on the list. NVIDIA graphics processors are used in 65 systems, while 3 use AMD GPUs. Intel’s Xeon Phi is the next most popular accelerator, which powers 23 of the Green500 systems. Despite the prevalence of accelerators at the top of the list, overall 406 systems rely on CPUs only.
 
China has 21 of the top 50 greenest supercomputers, while the US claims 8 such systems. Germany has 5 of the top 50 systems, with Japan and France each claiming 4 systems. Looking at the entire list, China has 168 systems, the US has 165, Japan has 29, Germany has 26, and France has 18.
 
The average energy efficiency in the current list is 1116.8 MFLOPS/Watt or a little over 1 GFLOPS/Watt. While Shoubu, the greenest supercomputer, is more than 6 times as efficient as the average, the goal of a 20 MW exaflop system would require an energy efficiency of 50 GFLOPS/Watt. Using the current trend line, the first 20 MW supercomputer capable of an exaflop would not appear until after 2022.
 
TOP 10 ENERGY-EFFICIENT SUPERCOMPUTERS IN JUNE 2016
 Listed below are the Green500’s energy-efficient supercomputers ranked from 1 to 10. 

 
Source: the Green500 List