The Green500 list states that it puts a premium on energy-efficient performance for sustainable supercomputing.The Green500 list ranks the top 500 supercomputers in the world by energy efficiency. A focus of “performance-at-any-cost computer operations” led to emergence of supercomputers that consume vast amounts of electrical power and produce so much heat that large cooling facilities must be constructed to ensure proper performance. In order to address this trend, the Green500 list states that it puts a premium on energy-efficient performance for sustainable supercomputing.

Currently, the Green500 has two releases per year: June and November. The inaugural list was released on November 15, 2007 at SC|07. As a complement to the TOP500, the unveiling of the Green500 “ushered in a new era where supercomputers can be compared by performance-per-watt.”

For decades, the notion of "performance" has been synonymous with "speed" (as measured in FLOPS, short for floating-point operations per second). This focus has led to the emergence of “supercomputers that consume egregious amounts of electrical power and produce so much heat that extravagant cooling facilities must be constructed to ensure proper operation. In addition, the emphasis on speed as the ultimate metric has caused other metrics such as reliability, availability and usability to be largely ignored,” the List site states. And this, in turn, has resulted in “an extraordinary increase in the total cost of ownership (TCO) of a supercomputer.”

In order to raise awareness to other performance metrics of interest (e.g., performance per watt and energy efficiency for improved reliability), the Green500 offers lists to encourage supercomputing stakeholders to ensure that supercomputers are only simulating climate change and not creating climate change.

World’s most energy-efficient system

On November 18, 2015, the Shoubu supercomputer from RIKEN maintained the top spot on the 18th edition of the List and claimed the title of the “most energy-efficient (or greenest) supercomputer in the world.” The Shoubu supercomputer, which surpassed the seven gigaflops/watt (billions of operations per second per watt) milestone in July 2015, also remains as the only supercomputer that has surpassed that mark. The TSUBAME-KFC/DL supercomputer from the GSIC Center at Tokyo Institute of Technology in Japan and the Lattice-CSC supercomputer from GSI Helmholtz Center in Germany grabbed second and third place, respectively, with both machines surpassing five gigaflops/watt.

History of The Green500

The Green500 began in April 2005 after a keynote talk by Dr. Wu-chun Feng at the IEEE IPDPS Workshop on High-Performance, Power-Aware Computing. The idea was then formally presented at the workshop a year later, with a paper and associated talk entitled "Making a Case for a Green500 List," [ paper ] [ talk ]. A subsequent presentation at Clusters and Computational Grids for Scientific Computing 2006, "Global Climate Warming? Yes … In The Machine Room," brought increased interest. Ultimately, the announcement of the Green500 was made at SC|06. One year later, at SC|07, the inaugural list was released.

Lead Investigators

Dr. Wu-chun Feng is an associate professor of Computer Science with a courtesy appointment in Electrical & Computer Engineering at Virginia Tech (VT). At VT, he directs the Synergy Laboratory, which conducts research at the synergistic intersection of systems software, middleware and application software; of particular note is his high-performance computing (HPC) research in the areas of green supercomputing, accelerator-based parallel computing, and bioinformatics.

Dr. Kirk W. Cameron is an associate professor of Computer Science at Virginia Polytechnic Institute and State University. He directs the SCAPE Laboratory at Virginia Tech where he pioneered the area of Green HPC to improve the efficiency of high-end systems. Prof. Cameron is on the editorial board and editor for the IEEE Computer "Green IT" column. He is an active consultant for the Energy Star program for Servers and a founding member of SPECPower, the first and foremost industry benchmark for power and performance.

Green 500 Lists

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