Testing. Testing? Testing! How RSEs can Assure Software Quality in Complex HPC Code Bases.

HPC software is often regarded simply as a tool to advance science and publish results. However, the process of developing and maintaining HPC software is getting more complex. Since the lifetime of a code outlasts the lifetime of an HPC cluster, porting and optimizing for a new system is always required. How can we improve and automate the workflow of development and maintenance? In this talk, we focus on the software engineering part of HPC code development. We describe how automated unit testing and continuous integration help to keep the software in a manageable state

Periodic Boundary Conditions and the Error-Controlled Fast Multipole Method

The simulation of pairwise interactions in huge particle ensembles is a vital issue in scientific research. Especially the calculation of long-range interactions poses limitations to the system size, since these interactions scale quadratically with the number of particles. Fast summation techniques like the Fast Multipole Method (FMM) can help to reduce the complexity to $\mathcal{O}$(N). This work extends the possible range of applications of the FMM to periodic systems in one, two and three dimensions with one unique approach. Together with a tight error control, this contribution enables the simulation of periodic particle systems for different applications without the need to know and tune the FMM specific parameters. The implemented error control scheme automatically optimizes the parameters to obtain an approximation for the minimal runtime for a given energy error bound

The Fast Multipole Method - Alternative Gradient Algorithm and Parallelization

This thesis describes the Fast Multipole Method (FMM). The method reduces the complexity of the Coulomb problem from O(N$^{2}$) to O(N) and is therefore called a fast Coulomb solver. The FMM is advantageous for the calculation of pairwise interactions, especially for large systems. This work is divided in three parts. The first part addresses the fundamentals of the FMM. The second part discusses the force calculation with the gradient. Two different implementations of the gradient are discussed. The last part shows the parallelization of the FMM. The procedure is described exemplarily for one pass