PLANETESIM: Fourier transformations in the Pencil Code

The simulation of weakly compressible turbulent gas ows with embedded particles is one of the main objectives of the
Pencil Code. While the code mostly deploys high order nite di erence schemes, portions of the code require the use of
Fourier space methods. This report describes an optimisation project to improve the performance of the parallel Fourier
transformation in the code. Certain optimisations which signi cantly improve the performance of the parallel FFT were
observed to have a negative impact on other parts of the code, such that the overall performance decreases. Despite this
challenge the project managed to improve the performance of the parallel FFT within the Pencil Code by a factor of
2.4 and the overall performance of the application by 8% for a project-relevant benchmark.