Format Optimization for Periodical Snapshot Output in CFD Simulation

Abstract

Computational Fluid Dynamics (CFD) simulation often needs to periodically output the intermediate results to files in the form of snapshots for visualization or restart, which seriously impacts the performance. Traditional CFD simulation takes ASCII format with typesetting in the snapshot output process, which results in precision loss of the data in the snapshot array and more storage space occupancy than the original binary format. In this paper, we propose the binary non-typesetting format optimization for the snapshot output in CFD simulation, aiming at eliminating the impact of ASCII format. In our optimization method, the snapshot array is output in binary format without typesetting. On one hand, it reserves the original binary precision in the output files, while the ASCII format always has precision loss, which seriously impacts the accuracy of CFD simulation; On the other hand, non-typesetting provide the opportunity of output the snapshot as a continuous memory block, which will signally improve the efficiency of the output. We design the multiply output mode framework for CFD applications through the combination of ASCII typesetting format and binary non-typesetting format. We implement this multiply output mode framework in the open source CFD software OpenFOAM. Experimental results on Tianhe-2 supercomputer demonstrate that our binary non-typesetting format optimization technique can achieve good optimization effect for the periodical snapshot output in CFD application.