PCMS: Parallel coupler for multimodel simulations
Description
This paper presents the Parallel Coupler for Multimodel Simulations (PCMS), a new GPU accelerated generalized framework for coupling simulation codes on leadership class supercomputers. PCMS includes distributed control and field mapping methods for up to five dimensions. For field mapping, PCMS can utilize discretization and field information to accommodate physics constraints. PCMS is demonstrated with a coupling of the gyrokinetic microturbulence code XGC with a Monte Carlo neutral transport code DEGAS2 and with a 5D distribution function coupling of an energetic particle transport code (GNET) to a gyrokinetic microturbulence code (GTC). A scaling study is also presented to stress the PCMS APIs and underlying rendezvous-based communication protocol implemented with ADIOS2. It demonstrates the high performance of the ADIOS2 SST engine using remote direct memory access versus the filesystem-based BP4 engine on up to 260 nodes of Frontier; 16 to 2048 processes for the application being scaled and a fixed 16 processes each for the coupler and the second application.