To meet the increasing demands of parallel scientific applications, supercomputers continue to grow in both scale and complexity. The fastest supercomputer in the world, El Capitan, features over a million CPU cores and tens of thousands of GPUs. Applications running on such large-scale systems are particularly susceptible to system noise or interference caused by the operating system (OS) and other services running on the same compute nodes as the application.

Coupling separately developed codes offers an attractive method for increasing the accuracy and fidelity of the computational models. Examples include the earth sciences and fusion integrated modeling. This paper describes the Framework Application for Core-Edge Transport Simulations (FACETS).