277MODEL COUPLING TOOLKIT THE MODEL COUPLING TOOLKIT: A NEW FORTRAN90 TOOLKIT FOR BUILDING MULTIPHYSICS PARALLEL COUPLED MODELS

Many problems in science and engineering are best simu-lated as a set of mutually interacting models, resulting in a coupled or multiphysics model. These models present challenges stemming from their interdisciplinary nature and from their computational and algorithmic complexi-ties. The computational complexity of individual models, combined with the popularity of the distributed-memory parallel programming model used on commodity micro-processor-based clusters, results in a parallel coupling problem when building a coupled model. We define and elucidate this problem and how it results in a set of requirements for software capable of simplifying the con-struction of parallel coupled models. We describe the package, the Model Coupling Toolkit (MCT), which we have developed to meet these general requirements and the specific requirements of a parallel climate model. We present the MCT programming model with illustrative code examples. We present representative results that meas-ure MCT’s scalability, performance portability, and a proxy for coupling overhead. Key words: Parallel computing, multiphysics, parallel cou-pling, coupled model