MONC performance portability
ARCHER2-eCSE03-12
PI: Dr Grenville MS Lister (NCAS-CMS, University of Reading)
Co-Is: Dr Nick Brown (EPCC, University of Edinburgh), Dr Adrian A Hill (UK Met Office), Dr Todd R Jones (University of Reading)
Technical staff: Dr Juan F Rodriguez Herrera (EPCC, University of Edinburgh)
Subject Area:
The Met Office NERC Cloud model (MONC) is a high-resolution atmospheric modelling code used throughout the UK by the Met Office and several UK universities. MONC is used primarily as a tool to develop computational representations of atmospheric processes through its capability to efficiently run at extremely high-resolution (O(a few metres)) with full inclusion of explicit physical processes, including comprehensive microphysical, aerosol, and radiative processes via CASIM and SOCRATES. The code forms a component of NERC research in multiple areas as a tool to aid development of parameterisations for use in large-scale climate and Numerical Weather Prediction (NWP) models, where parameterisation of subgrid-scale processes is essential on the grounds of computational cost. Parameterizations developed this way are implemented in climate and NWP models to better represent radiative and precipitation processes.
MONC is a FORTRAN code initially developed jointly by EPCC and the Met Office. It is an MPI code that incorporates a bespoke IO system to handle variable length time stepping.
The work undertaken in this project had three main objectives: (i) to port MONC to the ARCHER2 architecture and explore the space of available compilers; (ii) to expand the applicability of the code to general MONC problem sizes; (iii) to relax a built-in restriction on halo size.
Progress has been made in all three objectives. MONC builds and runs on ARCHER2 with both GNU and CCE compilers. The objective to enable arbitrary MONC problem sizes has been achieved through replacement of the FFTE dependency with FFTPACK. Strong and weak scaling results indicate that the modified model performs acceptably.
Work to relax the halo size restriction has been partially successful, with relaxation now possible for specific MONC configurations that do not involve halo swapping in the surface boundary condition.
Information about the code
MONC (Met Office NERC Cloud model) is a high-resolution code for the modelling of clouds and atmospheric flows at large scale. It is used throughout the UK by the Met Office and several UK universities. The code was initially developed jointly by EPCC and the Met Office. It was developed in Fortran and uses MPI for parallelism.
MONC is available at the Met Office Science Repository Service – potential users should contact NCAS CMS to arrange access.