A Multiprocessor Ocean General Circulation Model Using Message Passing

Abstract

Numerical models of the ocean are widely used to study the physics, chemistry, and biology of the ocean and its effect on climate. Unfortunately limits in available computer power often restrict the length of model 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 used either with clusters of workstations or with the new generation of array-processor computers. This paper reports on a new ocean general circulation model code that can be used on either a cluster of workstations or an array-processor computer. The model consists of one master control process and a number of slave oceanic processes, each of the latter being responsible for one subregion of the full ocean. The shapes of the subregions are variable allowing the computation and message passing load to be shared equally among processes. The code has also been 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 includes fully functioning archive, restart, snapshot, meteorological field updating, and progress reporting facilities. The model code has been tested on a cluster of Unix workstations and on a Cray T3D. On the workstation cluster, message passing delays affect performance, but on the Cray T3D a very high level of parallelism is achieved.