CaDS Seminar 2022 - Sep. 6

Stjepan Pozgaj (SDL Climate)

Accelerating numerical simulation of multiple scattering for radiation transport

Abstract:
The Juelich Rapid Spectral Simulation Code (JURASSIC) is a fast radiative transfer model for the analysis of atmospheric remote sensing measurements in the mid-infrared spectral region. It is used to derive the state of the atmosphere from the measurements. It was written in C and features an MPI/OpenMP hybrid parallelization for use on supercomputers. JURASSIC-GPU was developedby porting JURASSIC to GPUs using the CUDA programming language. To incorporate particles into the model, scattering of the infrared radiation on the particles was accounted for in the JURASSIC-scatter model, but this model so far did not benefit from tuningand acceleration of the reference model. The goal of the work in this thesis was to accelerate the JURASSIC-scatter forward model. It was done by combining it with JURASSIC-GPU. The implementation that uses both models was benchmarked on JUWELS - oneof the world's top supercomputers, and the achieved speedup was around 10x. After that, to remove code duplicates and to make the code easier to understand and maintain, JURASSIC-scatter and JURASSIC-GPU were merged into the new unified code projectnamed JURASSIC-unified. This unified implementation has even better performance - it is around 24x faster than the initial JURASSIC-scatter implementation. In addition to a new feature, the JURASSIC-unified project was adapted so that even the JURASSIC reference project can use it as a library.