Performance portability of Ensemble Kalman Filter using C++ senders/receivers

Asahi, Yuichi   ; Hasegawa, Yuta   ; Padioleau, T.*; Millan, A.*; Bigot, J.*; Grandgirard, V.*; Obrejan, K.*

Generally, production-ready scientific simulations consist of many different tasks including computations, communications and file I/O. Compared to the accelerated computations with GPUs, communications and file I/O would be slower which can be major bottlenecks. It is thus quite important to manage these tasks concurrently to suppress these costs. In the present talk, we employ the proposed language standard C++ senders/receivers to mask the costs of communications and file I/O. As a case study, we implement a 2D turbulence simulation code with the local ensemble transform Kalman filter (LETKF) using C++ senders/receivers. In LETKF, the mock observation data are read from files followed by MPI communications and dense matrix operations on GPUs. We demonstrate the performance portable implementation with this framework, while exploiting the performance gain with the introduced concurrency.