Communication-overlap techniques for improved strong scaling of gyrokinetic Eulerian code beyond 100k cores on the K-computer

井戸村 泰宏; 仲田 資季; 山田 進; 町田 昌彦; 今村 俊幸*; 渡邉 智彦*; 沼波 政倫*; 井上 晃*; 堤 重信*; 三吉 郁夫*; et al.

International Journal of High Performance Computing Applications, 28(1), p.73 - 86, 2014/02

https://doi.org/10.1177/1094342013490973

A plasma turbulence research based on five dimensional (5D) gyrokinetic simulations is one of the most critical and demanding issues in fusion science. To pioneer new physics regimes both in problem sizes and in time scales, an improvement of strong scaling is essential. In this work, the strong scaling and the parallel efficiency of a gyrokinetic toroidal 5D Eularian code GT5D is dramatically improved by novel developing communication overlap techniques. On the K-computer, excellent strong scaling is achieved beyond 100 k cores with keeping the sustained performance of 10% ( 307 TFlops using 196,608 cores), and simulations for next generation large-scale fusion experiments are significantly accelerated.