1 Performance Modeling the Earth Simulator and ASCI Q

This work gives a detailed analysis of the relative performance between the Earth Simulator and ASCI Q. The Earth Simulator uses vector processing nodes interconnected using a single-stage cross-bar network, whereas ASCI Q is built using superscalar Alpha microprocessors and the Quadrics Elan3 interconnection network. The performance that can be achieved on a system results from an interplay of the system characteristics, application requirements and scalability behavior. Detailed performance models are used here to predict the performance of two codes representative of ASCI computations, namely SAGE and Sweep3D. The performance models encapsulate fully the behavior of these codes and have been previously validated on many large-scale systems. They do not require access to a full sized system but rather rely on characteristics of the system as well as knowledge of the achievable single-processor performance. The models are used to compare the performance of the two machines. One result of this analysis is to size an Alpha System that will have the same performance as the Earth Simulator.