I/O Performance Evaluation of a Memory-Saving DNS Code on SX-Aurora TSUBASA

Direct numerical simulation (DNS) by spectral methods is widely used to reveal turbulence properties because of its high accuracy. DNS with a larger number of grid points than simulations conducted to date, however, requires a large amount of computation time and memory capacity. Therefore, DNS with a large number of grid points is not realistic, even if state-of-the-art supercomputers are used. In this paper, in order to execute a DNS with a larger number of grid points, a memory-saving DNS code has been developed to solve the memory capacity constraint at the expense of increased CPU time. Variables in the code are subdivided and stored in multiple temporary files and are processed sequentially during the calculations. The DNS code has been carried out as an early performance evaluation on SX-Aurora TSUBASA equipped with synchronous and asynchronous input and output (I/O) functions. The results clarified that the synchronous I/O performance outperformed the asynchronous I/O performance. The shortest calculation time was achieved using the synchronous I/O to eight temporary files on solid state drives.