Abstract
In this study, we conducted field measurements of energy consumption for two supercomputers and one cluster computer, and studied the appropriate definition of energy efficiency for high performance computers. We found that unlike automobiles and air-conditioners, energy use of a high performance computer has no proportional relationship with the amount of its utility. Taking into account the fact that the stock of high performance computers has inverse relationship with their performances, the appropriate definition of energy efficiency should be the ratio between performance and average power requirement. Because the energy efficiency based on theoretical performance does not reflect the actual energy efficiency, practical performance should be used in the definition of energy efficiency.
