Paul Gessinger
Senior Applied Fellow at CERN
Vernier, Geneva, Switzerland
Summary
👤
Senior🎓
Top SchoolPaul Gessinger is a Senior Applied Fellow at CERN with 11 years of experience building high-performance software for charged particle track reconstruction and coordinating teams on next-generation tracking detectors and GPU algorithms. He holds a PhD in Physics and has a strong track record in both research-driven data analysis (searches for long-lived particles) and production-grade C++ software engineering. An active open-source contributor, Paul helps maintain scientific packaging in spack and has improved geometry, material assignment and testing infrastructure in the Acts tracking toolkit, demonstrating attention to portability and cross-compiler compatibility. Earlier careers in web development and freelance work give him full-stack intuition that informs robust backend design and visualization work (notably contributions to ROOT’s TRatioPlot). Based in Vernier, Geneva, he blends experimental physics insight with pragmatic engineering—equally comfortable debugging compiler toolchains as optimizing GPU-enabled reconstruction code.
11 years of coding experience
9 years of employment as a software developer
Bachelor of Science (BSc), Physics, Bachelor of Science (BSc), Physics at Johannes Gutenberg University Mainz
German, English
Stackoverflow
163reputation
9kreached
4answers
6questions
Github Skills (28)
unit-testing10
algorithms10
root-view10
c-language10
visualization10
geometry10
package-management10
cmake10
data-structure10
document-root10
data-structures10
visualizations10
cprogramming-language10
data-analysis10
graphic9
Programming languages (19)
Github contributions (5)
acts-project/acts
Aug 2017 - Jan 2023
Experiment-independent toolkit for (charged) particle track reconstruction in (high energy) physics experiments implemented in modern C++
Role in this project:
Back-end Developer
Back-end DeveloperContributions:87 releases, 3021 reviews, 1579 commits in 5 years 6 months
Contributions summary:Paul primarily worked on implementing core features related to geometry handling within the Acts project. This included developing a system for material assignment and creating a new interface for track parameters in the core component. The user also contributed to the testing infrastructure with new features like enabling the analysis of performance and implementing a test to verify the output of the code. Furthermore the user worked on internal improvements in existing data structures.
physics-enginephysics-experimentreconstructionphysicsparticle
spack/spack
Mar 2020 - Mar 2025
A flexible package manager that supports multiple versions, configurations, platforms, and compilers.
Role in this project:Backend Developer & Package Maintainer
Backend Developer & Package MaintainerContributions:20 reviews, 11 PRs, 50 comments in 5 years 1 month
Contributions summary:Paul primarily contributes to the `spack/spack` repository by modifying package definitions and build configurations for scientific software. Their work involves patching existing packages, adding new packages like SoQt, and resolving dependency issues for various scientific computing tools such as ROOT, Pythia8, and geomodel. Furthermore, the user addresses compiler compatibility issues, specifically related to C++ standards and compiler versions, to ensure the portability and build success of the packages across different environments.
compilerspythonradiussplatformslinux
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