Performance evaluation of block-structured Poisson solver on GPU, CPU, and ARM processors

Onodera, Naoyuki   ; Idomura, Yasuhiro   ; Asahi, Yuichi   ; Hasegawa, Yuta   ; Shimokawabe, Takashi*; Aoki, Takayuki*

We develop a multigrid preconditioned conjugate gradient (MG-CG) solver for the pressure Poisson equation in a two-phase flow CFD code JUPITER. The code is written in C++ and CUDA to keep the portability on multi-platforms. The main kernels of the CG solver achieve reasonable performance as 0.4 0.75 of the roofline performances, and the performances of the MG-preconditioner are also reasonable on NVIDIA GPU and Intel CPU. However, the performance degradation of the SpMV kernel on ARM is significant. It is confirmed that the optimization does not work if any functions are included in the loop.