The Scalable Modeling System: directive-based code parallelization for distributed and shared memory computers

A directive-based parallelization tool called the Scalable Modeling System (SMS) is described. The user inserts directives in the form of comments into existing Fortran code. SMS translates the code and directives into a parallel version that runs efficiently on shared and distributed memory high-performance computing platforms including the SGI Origin, IBM SP2, Cray T3E, Sun, and Alpha and Intel clusters. Twenty directives are available to support operations including array re-declarations, inter-process communications, loop translations, and parallel I/O operations. SMS also provides tools to support incremental parallelization and debugging that significantly reduces code parallelization time from months to weeks of effort. SMS is intended for applications using regular structured grids that are solved using finite difference approximation or spectral methods. It has been used to parallelize 10 atmospheric and oceanic models, but the tool is sufficiently general that it can be applied to other structured grids codes. Recent performance comparisons demonstrate that the Eta, Hybrid Coordinate Ocean model and Regional Ocean Modeling System model, parallelized using SMS, perform as well or better than their OpenMP or Message Passing Interface counterparts.