The November 2013 release of the Green500 list was announced today at the SC13 conference in Denver, Colorado. Continuing the trend from previous years, heterogeneous supercomputing systems totally dominate the top 10 spots of the Green500.

A heterogeneous system uses computational building blocks that consist of two or more types of “computing brains.” These types of computing brains include traditional processors (CPUs), graphics processing units (GPUs), and co-processors. In this edition of the Green500, one system smashes through the 4-billion floating-point operation per second (gigaflops) per watt barrier.

TSUBAME-KFC, a heterogeneous supercomputing system developed at the Tokyo Institute of Technology (TITech) in Japan, tops the list with an efficiency of 4.5 gigaflops/watt. Each computational node within TSUBAME-KFC consists of two Intel Ivy Bridge processors and four NVIDIA Kepler GPUs. In fact, all systems in the top ten of the Green500 use a similar architecture, i.e., Intel CPUs combined with NVIDIA GPUs. Wilkes, a supercomputer housed at Cambridge University, takes the second spot. The third position is filled by the HA-PACS TCA system at the University of Tsukuba. Of particular note, this list also sees two petaflop systems, each capable of computing over one quadrillion operations per second, achieve an efficiency of over 3 gigaflops/watt, namely Piz Daint at Swiss National Supercomputing Center and TSUBAME 2.5 at Tokyo Institute of Technology. Thus, Piz Daint is the greenest petaflop supercomputer on the Green500. As a point of reference, Tianhe-2, the fastest supercomputer in the world according to the Top500 list, achieves an efficiency of 1.9 gigaflops/watt.

This list marks a number of “firsts” for the Green500. It is the first time that a supercomputer has broken through the 4 gigaflops/watt barrier. Second, it is first time that all of the top 10 systems on the Green500 are heterogeneous systems. Third, it is the first time that the average of the measured power consumed by the systems on the Green500 dropped with respect to the previous edition of the list. “A decrease in the average measured power coupled with an overall increase in performance is an encouraging step along the trail to exascale,” noted Wu Feng of the Green500. Fourth, assuming that TSUBAME-KFC’s energy efficiency can be maintained for an exaflop system, it is the first time that an extrapolation to an exaflop supercomputer has dropped below 300 megawatts (MW), specifically 222 MW. “This 222-MW power envelope is still a long way away from DARPA’s target of an exaflop system in the 20-MW power envelope,” says Feng.

Starting with this release, the Little Green500 list only includes machines with power values submitted directly to the Green500. In fact, there are more than 400 systems that have submitted directly to the Green500 over the past few years. As in previous years, the Little Green500 list has better overall efficiency than the Green500 list on average.

Earlier this year, the Green500 adopted new methodologies for measuring the power of supercomputing systems and providing a more accurate representation of the energy efficiency of large-scale systems. In June 2013, the Green500 formally adopted measurement rules (a.k.a. “Level 1” measurements), developed in cooperation with the Energy-Efficient High-Performance Computing Working Group (EE HPC WG). Moreover, power-measurement methodologies with higher precision and accuracy were developed as a part of this effort (a.k.a. “Level 2” and “Level 3” measurements). With growing support and interest in the energy efficiency of large-scale computing systems, the Green500 is welcoming two more submissions at Level 2 and Level 3 than in the previous edition of the Green500 list. Of particular note, Piz Daint, the greenest petaflop supercomputer in the world, submitted the highest-quality Level 3 measurement.

The Green500 has provided a ranking of the most energy-efficient supercomputers in the world since November 2007. For decades, the notion of supercomputer “performance” has been synonymous with “speed.” This particular 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, when there is an emphasis on speed as the ultimate metric, it often comes at the expense of other performance metrics, such as energy efficiency, reliability, availability, and usability. As a result, there has been an extraordinary increase in the total cost of ownership (TCO) of a supercomputer. Consequently, the Green500 seeks to raise the awareness in energy efficiency of supercomputing and to drive it as a first-order design constraint on par with speed.

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Source: The Green500