Parallel computation of the Regional Ocean Modeling System

The Regional Ocean Modeling System (ROMS) is a regional ocean general circulation modeling system solving the free surface, hydrostatic, primitive equations over varying topography. It is free software distributed worldwide for studying both complex coastal ocean problems and the basin-to-global scale ocean circulation. The original ROMS code could only be run on shared-memory systems. With the increasing need to simulate larger model domains with finer resolutions and on a variety of computer platforms, there is a need in the ocean-modeling community to have a ROMS code that can be run on any parallel computer ranging from 10 to hundreds of processors. Recently, we have explored parallelization for ROMS using the Message-Passing Interface (MPI) programming model. In this paper, we present an efficient parallelization strategy for such a large-scale scientific software package, based on an existing shared-memory computing model. In addition, we discuss scientific applications and clata-performance issues on a couple of SGI systems, including Columbia, the world's third-fastest supercomputer.