The Message Passing Version of the Parallel Community Climate Model

J. B. Drake, R. E. Flanery, D. W. Walker, P. H. Worley

Mathematical Sciences Section

Oak Ridge National Laboratory

P. O. Box 2008

Oak Ridge, TN 37831-6367

U. S. A.

I. T. Foster, J. G. Michalakes, R. L. Stevens

Mathematics and Computer Science Division

Argonne National Laboratory

9700 South Cass Avenue

Argonne, IL 60439

U. S. A.

J. J. Hack and D. L. Williamson

National Center for Atmospheric Research

1850 Table Mesa Drive

Boulder, CO 80303

U. S. A.

Abstract

This paper is a brief review of a parallel version of the NCAR Community Climate Model, CCM2, implemented for MIMD massively parallel computers using a message-passing paradigm. The parallel implementation was developed on an Intel iPSC/860 with 128 processors and on the Intel Delta with 512 processors, and the initial target platform for the production version of the code is the Intel Paragon with 2048 processors. Because the implementation uses a standard, portable, message-passing library, the code can be easily ported to other multiprocessors supporting a message-passing paradigm, or run on machines distributed across a network.

The parallelization strategy used is to decompose the problem domain into geographical patches and assign each processor to do the computation associated with a distinct subset of patches. With this decomposition, the physics calculations involve only grid points and data local to a processor and are performed in parallel. Using parallel algorithms developed for the semi-Lagrangian transport, the fast Fourier transform and the Legendre transform, both physics and dynamics are computed in parallel with minimal data movement and modest change to the original CCM2 sourse code.

J. B. Drake, R. E. Flanery, P. H. Worley, D. W. Walker, I. T. Foster, J. G. Michalakes, R. L. Stevens, J. J. Hack and D. L. Williamson, The Message Passing Version of the Parallel Community Climate Model, in Parallel Supercomputing in Atmispheric Science: Proceedings of the Fifth ECMWF Workshop on the Use of Parallel Processors in Meterology, held November 23-25, 1992. Edited by G.-R. Hoffmann and T. Kauranne. Published by World Scientific Publishing, 1993.