FD4: A Framework for Highly Scalable Load Balancing and Coupling of Multiphase Models

More and more detailed simulation codes are developed promoted by the growing capability of high performance computers and the increasing knowledge about the underlying processes. This includes multiphase and multiphysics simulations as well as the coupling of multidisciplinary models. This paper introduces the framework FD4 (Four-Dimensional Distributed Dynamic Data structures), which enables highly scalable implementations of multiphase models. The separation of the data structures for the single phases allows the use of different partitionings and also dynamic load balancing, which is essential to efficiently utilize high performance computers. The application of FD4 for an atmospheric modeling system with a detailed description of cloud processes successfully eliminates the load imbalance with a moderate overhead of 5% at 32k processors.