ジャイロ運動論的シミュレーションにおける並列FFTの通信マスク手法

Masking communication costs of parallel FFT in gyrokinetic Vlasov simulations

前山 伸也; 渡邉 智彦*; 井戸村 泰宏   ; 仲田 資季; 沼波 政倫*; 石澤 明宏*

Maeyama, Shinya; Watanabe, Tomohiko*; Idomura, Yasuhiro; Nakata, Motoki; Nunami, Masanori*; Ishizawa, Akihiro*

We have been developed the electromagnetic version of the gyrokinetic Vlasov simulation code GKV on the plasma simulator. The code has to solve both gyrokinetic ions and electrons, which leads expensive computational costs. Parallel two-dimensional FFT is recently implemented to speed up the GKV code. However, communication costs of data transpose become dominant and degrade the computational efficiency as the number of parallelization increases. To achieve more efficient computations, computation-communication overlap by means of the MPI/OpenMP hybrid parallelization is developed, which enables overlap of computations and blocking collective communications as well as non-blocking communications. We examine the effect of the overlap method on the computational cost and demonstrate the speed-up and improvement of the strong scaling of the GKV code.