DiRong1.0: A distributed implementation for improving routing network generation in model coupling

A fundamental functionality of model coupling in an Earth system model is to efficiently handle data transfer between component models. An approach of M × N communication following a routing network has been used widely used for data transfer, and routing network generation becomes a major step required to initialize data transfer functionality. Some existing coupling software such as the Model Coupling Toolkit (MCT) and the existing versions of the Community Coupler (C-Coupler) employ a global implementation of routing network generation that relies on gather-broadcast communications, which can be very inefficient under a case of a large number of processes. This is an important reason why the initialization cost of a coupler increases with the number of processor cores. In this paper, we propose a "distributed implementation for routing network generation, version 1.0"(DiRong1.0), which does not introduce any gather-broadcast communication. Empirical evaluations show that DiRong1.0 is much more efficient than the global implementation. DiRong1.0 has already been implemented in C-Coupler2, and we believe that some other couplers can also benefit from it.