Ten organising principles for coupling in multiphysics and multiscale models

Computational science faces new challenges posed by multiphysics and multiscale, or more generally put, coupled models. These systems are composites formed from separate subsystem models that interact via data exchanges. These data dependencies pose a coupling problem, and on distributed memory computers, a parallel coupling problem. This article presents a definition of terms and a set of organising principles for the coupling and parallel coupling problems. It is meant as a first step towards creating a theory of coupled models. These principles are then employed in a case study of a coupled climate model and offer remarkable insight into its structure. References J. R. Cary, J. Candy, R. H. Cohen, S. Krasheninnikov, D. C. McCune, D. J. Estep, J. Larson, A. D. Malony, P. H. Worley, J. A. Carlsson, A. H. Hakim, P. Hamill, S. Kruger, S. Muzsala, A. Pletzer, S. Shasharina, D. Wade-Stein, N. Wang, L. McInnes, T. Wildey, T. Casper, L. Diachin, T. Epperly, T. D. Rognlien, M. R. Fahey, J. A. Kuehn, A. Morris, S. Shende, E. Feibush, G. W. Hammett, K. Indireshkumar, C. Ludescher, L. Randerson, D. Stotler, A. Yu Pigarov, P. Bonoli, C. S. Chang, D. A. D'Ippolito, P. Colella, D. E. Keyes, R. Bramley, and J. R. Myra. Introducing facets, the framework application for core-edge transport simulations. Journal of Physics Conference Series, 78:0120086, 2007. W. D. Collins, C. M. Bitz, M. L. Blackmon, G. B . Bonan, C. S. Bretherton, J. A. Carton, P. Chang, S. C. Doney, J. J. Hack, T. B. Henderson, J. T. Kiehl, W. G. Large, D. S. McKenna, B. D. Santer, and R. D. Smith. The community climate system model: CCSM3. Journal of Climate, 19(11):2122--2143, 2006. Anthony P. Craig, Brian Kaufmann, Robert Jacob, Tom Bettge, Jay Larson, Everest Ong, Chris Ding, and Helen He. cpl6: The new extensible high-performance parallel coupler for the community climate system model. Int. J. High Perf. Comp. App., 19(3):309--327, 2005. R. Diestel. Graph Theory. Springer, New York, third edition, 2006. Ian Foster. Designing and Building Parallel Programs: Concepts and Tools for Parallel Software Engineering. Addison Wesley, Reading, Massachusetts, 1995. CCSM Software Engineering Group. CCSM research tools: CCSM3.0 coupler v6.0 documentation. http://www.ccsm.ucar.edu/models/ccsm3.0/cpl6/, 2004. W. Joppich, M. Kurschner, and the MpCCI Team. MpCCI---a Tool for the Simulation of Coupled Applications. Concurrency and Computation: Practice and Experience, 18(2):183--192, 2006. doi:10.1002/cpe.913 Jay Larson, Robert Jacob, and Everest Ong. The model coupling toolkit: A new Fortran90 toolkit for building multi-physics parallel coupled models. Int. J. High Perf. Comp. App., 19(3):277--292, 2005. WRF Development Team. Weather research and forecasting (WRF) model web site. http://wrf-model.org/, 2006