LFRic: Meeting the challenges of scalability and performance portability in Weather and Climate models

TL;DR

LFRic is a new weather and climate modeling system designed for exascale computing, emphasizing modularity, performance portability, and scalability through innovative software infrastructure and code generation tools.

Contribution

The paper introduces LFRic's architecture, its object-oriented infrastructure, and the PSyclone tool for generating portable parallel code across diverse architectures.

Findings

Strong scaling demonstrated in preliminary results

Hybrid MPI/OpenMP outperforms pure MPI

Separation of concerns enhances performance portability

Abstract

This paper describes LFRic: the new weather and climate modelling system being developed by the UK Met Office to replace the existing Unified Model in preparation for exascale computing in the 2020s. LFRic uses the GungHo dynamical core and runs on a semi-structured cubed-sphere mesh. The design of the supporting infrastructure follows object orientated principles to facilitate modularity and the use of external libraries where possible. In particular, a `separation of concerns' between the science code and parallel code is imposed to promote performance portability. An application called PSyclone, developed at the STFC Hartree centre, can generate the parallel code enabling deployment of a single source science code onto different machine architectures. This paper provides an overview of the scientific requirement, the design of the software infrastructure, and examples of PSyclone usage. Preliminary performance results show strong scaling and an indication that hybrid MPI/OpenMP performs better than pure MPI.