Abstract:

This study applies Tuning and Analysis Utilities (TAU) to analyze the parallel performance of the unstructured grid FiniteVolume Coastal Ocean Model (FVCOM) version 2.6 based on Message Passing Interface (MPI). Examples of ShenHu Bay FVCOM tidal models, with low resolutions (2108 and 10378 nodes) and high resolutions (15347 and 26033 nodes), are  tested using various processes on a linux cluster (Intel Xeon CPU E5450 and 10G InfiniBand). The results show that the advection subroutines occupied large proportion of running time as the models ran on a single process. The speed up of each test is examined; the grid number which affected the parallel performance as the models ran on multiple processes. Under the hardware condition of this study, each test had an optimal number of processes, which are  32 for low resolutions and 64 for high resolutions. The optimal number of processes is increased as the resolution increased. The total run time started increasing as the number of processes exceeded the optimal number. The TAU analysis shows that it is mainly due to the increasing times of calling MPI_Waitany subroutine so that the barrier time increased nearly proportionally to the total time, which provides information to improve the parallel performance for FVCOM in the future.

Key words: FVCOM;TAU;performance analysis;parallel computing