A MULTIPROCESSOR OCEAN GENERAL-CIRCULATION MODEL USING MESSAGE-PASSING

Numerical models of the ocean are widely used to study the physics, ch emistry, and biology of the ocean and its effect on climate. Unfortuna tely limits in available computer power often restrict the length of m odel runs and the amount of detail that can be included in the models. For this reason there is interest in developing a code that can be us ed either with clusters of workstations or with the new generation of array-processor computers. This paper reports on a new ocean general c irculation model code that can be used on either a cluster of workstat ions or an array-processor computer. The model consists of one master control process and a number of slave oceanic processes, each of the l atter being responsible for one subregion of the full ocean. The shape s of the subregions are variable allowing the computation and message passing load to be shared equally among processes. The code has also b een designed so that message passing between processes is asynchronous . This allows the message passing and computation to be overlapped and helps to prevent the development of bottlenecks. Finally, the code in cludes fully functioning archive, restart, snapshot, meteorological fi eld updating, and progress reporting facilities. The model code has be en tested on a cluster of Unix workstations and on a Gray T3D. On the workstation cluster, message passing delays affect performance, but on the Gray T3D a very high level of parallelism is achieved.