M × N Communication and Parallel Interpolation in Community Climate System Model Version 3 Using the Model Coupling Toolkit

TLDR

The Model Coupling Toolkit (MCT) is a library for building parallel coupled models, addressing the M × N data‑transfer challenge that arises when Community Climate System Model submodels—each a separate parallel application with its own domain decomposition—require efficient communication to support interpolation algorithms. MCT was developed as a generalized solution to create a parallel coupler for the Community Climate System Model and other parallel coupled models, and this paper describes its data‑transfer infrastructure. The paper details MCT’s implementation of a data‑transfer infrastructure that enables parallel coupling between disjoint processor sets. MCT scales satisfactorily with added processors, though performance depends on submodel decomposition, and its infrastructure offers flexible, high‑performing tools for interoperability between parallel applications.

Abstract

The Model Coupling Toolkit (MCT) is a software library for constructing parallel coupled models from individual parallel models. MCT was created to address the challenges of creating a parallel coupler for the Community Climate System Model (CCSM). Each of the submodels that make up CCSM is a separate parallel application with its own domain decomposition, running on its own set of processors. This application contains multiple instances of the M × N problem, the problem of transferring data between two parallel programs running on disjoint sets of processors. CCSM also requires efficient data transfer to facilitate its interpolation algorithms. MCT was created as a generalized solution to handle these and other common functions in parallel coupled models. Here we describe MCT’s implementation of the data transfer infrastructure needed for a parallel coupled model. The performance of MCT scales satisfactorily as processors are added to the system. However, the types of decompositions used in the submodels can affect performance. MCT’s infrastructure provides a flexible and high-performing set of tools for enabling interoperability between parallel applications.