On exchange with eSSENCE: Philipp Birken

In the winter of 2025, Philipp Birken, Professor of Numerical Analysis and Scientific Computing at Lund University, participated in an exchange visit within the eSSENCE exchange program. The visit took place at Uppsala University, where he collaborated with Roman Iakymchuk, Associate Professor at the Department of Information Technology. Now that the visit has concluded, we took the opportunity to ask him a few questions about his experiences and impressions from the exchange.

What concrete outcomes have resulted from your collaboration within the project?
— As a concrete result of the exchange, we started measuring energy to solution on one core of the european supercomputer LUMI using the SLURM interface. We considered a sparse linear system with up to 250.000 unknowns, solved with a sparse direct solver. The images shows time to solution and energy to solution over the number of unknowns. As expected for this case, the two curves have the same behavior. It is therefore a validation of our approach to measure energy to solution.

How has the eSSENCE Exchange collaboration contributed to your network?

— The Exchange has allowed Roman and me to intensify our collaboration. Additionally, it allowed me to have number of discussions with other eSSENCE researchers from Uppsala. As an example, we discussed a coordinated swedish effort for participation in the Euro-HPC masterprogram.

How has the collaboration contributed to your research?

— Roman and I started working on our project concretely, allowing us to define approaches, test cases, and methods concretely. This resulted in first result that validates our approach. Additionally, we discussed further concrete steps. These have led to an agreement about usage of the czech supercomputer with a different tool for measuring energy, and to further discussions about personnel. We now have a PhD student in Lund working on the project, and a Researcher from Environment and Climate Change Canada (ECCC).

What do you hope the collaboration will lead to in the long term?

Our ambition is to help establish energy to solution as an alternative way of describing performance of numerical methods.