Software Engineer - High-Performance Computing (EP-SFT-2026-137-LD)

Company Description
At CERN , the European Organization for Nuclear Research, physicists and engineers are probing the fundamental structure of the universe. Using the world's largest and most complex scientific instruments, they study the basic constituents of matter - fundamental particles that are made to collide together at close to the speed of light. The process gives physicists clues about how particles interact, and provides insights into the fundamental laws of nature.

Introduction
This role focuses on improving and evolving software developed in the EP-SFT group such as Geant4 and ROOT , two core software frameworks used for particle physics simulation and data analysis at CERN and laboratories worldwide. The position involves optimising and redesigning key components to run efficiently on modern high-performance computing systems, with a strong emphasis on GPU acceleration and large-scale parallel processing. Responsibilities include contributing to next-generation technologies such as AdePT for GPU-based particle transport, enhancing performance for exabyte-scale data processing, and developing tools for profiling, testing, and validation. Working at the intersection of HPC, C++ software engineering, and experimental physics, the role directly supports future research initiatives including the High-Luminosity LHC and the Future Circular Collider.

Functions

• Devise Performance Strategy: Define and execute the performance roadmap for Geant4 and ROOT, also focusing on GPU architectures (CUDA, SYCL) and the exploitation of advanced features of programming languages, such as C++.
• Hands-on Development: Implement and refactor critical hot loops, memory layouts, and kernel launches. Use state-of-the-art tools to identify and eliminate bottlenecks.
• Take part in the overall organisation of data simulation, processing, and analysis activities within the EP-SFT group’s
• Projects, including work planning, the organisation of workshops and trainings, and representing the projects and their vision.
• Engage with the projects’ user communities, foster collaboration within the SFT group, the EP department, and CERN, and encourage external contributions from laboratories, universities, and other partners.
• Supervise team members and coordinate activities related to the EP-SFT data simulation, processing, and analysis projects.

Qualifications
Master's degree or PhD or equivalent relevant experience in the field of Computer Science, Physics or a related field.

Experience:

• Demonstrated experience in high-performance computing, including GPU programming and C++ (template metaprogramming, SIMD, cache-aware design).
• A proven track record of optimising large (100k+ line) scientific or data-intensive software projects.
• Solid experience with performance profiling tools (e.g., Nsight, VTune, perf, Valgrind), debugging tools (GDB, LLDB), and continuous integration performance regression testing.
• Familiarity with Geant4, ROOT, or other high-energy physics simulation and analysis frameworks would be an advantage.
• Experience contributing to LLVM/Clang or compiler-level optimisation work is considered an asset.
• Knowledge of Monte Carlo particle transport algorithms or statistical data analysis is advantageous.
• A publication record or invited talks at major conferences (e.g., Supercomputing, CHEP, IEEE/ACM performance workshops) is considered a plus.
• Experience in supervising and coordinating external contributors would be desirable.

Technical competencies:

• Development of application software, advanced C++ and Python.
• Testing, diagnosing and optimisation of software, gPU profiling, memory optimisation, parallel debugging.
• Knowledge of programming techniques and languages, parallel programming techniques such as CUDA, std::thread, TBB, or MPI. Experience with the usage of Clang and LLVM would be considered an advantage.
• Knowledge and application of software life-cycle tools and procedures (GitLab CI, JIRA, CMake, Spack) would be considered an advantage.

Behavioural competencies:

• Achieving Results: having a structured and organised approach towards work; being able to set priorities and plan tasks with results in mind.
• Solving Problems: finding the information needed to solve problems; making objective judgements based on all the facts available.
• Communicating Effectively: expressing opinions, ideas and suggestions with conviction and in a logical/structured manner; keeping to the point.
• Learning and Sharing Knowledge: sharing knowledge and expertise freely and willingly with others; coaching others to ensure knowledge transfer.
• Demonstrating Flexibility: adapting quickly and resourcefully to shifting priorities and requirements.

Language skills:
Spoken and written English, with a commitment to learn French.

Additional Information
Eligibility and closing date:
Diversity

has been an integral part of CERN's mission since its foundation and is an established value of the Organization. Employing a diverse workforce is central to our success. We welcome applications from all Member States and Associate Member States .

This vacancy will be filled as soon as possible, and applications should normally reach us no later than Se telefonnummer på jobbank.dk at 23:59 CEST.
Employment Conditions
Contract type: Limited duration contract (5 years). Subject to certain conditions, holders of limited-duration contracts may apply for an indefinite position.

Working Hours: 40 hours per week

Job Flexibility: Hybrid

This position involves:

• Work during nights, Sundays and official holidays, when required by the needs of the Organization.

Job grade: 6-7

Job reference: EP-SFT-2026-137-LD

Field of work: Software Engineering and IT

Benchmark Job Title: Computing Engineer

Global Benefits

• A competitive salary (tax free), increasing in line with your years of relevant experience.
• 30 days of paid leave per year plus 2 weeks annual closure.
• Coverage by CERN’s comprehensive health insurance scheme (for yourself, your spouse and children), and membership of the CERN Pension Fund.
• Family, child and infant monthly allowances depending on your individual circumstances.
• A relocation package (installation grant, removal, travel expenses) depending on your individual circumstances.
• Possibility to extend your contract up to 8 years + eligibility for indefinite contract tenure.

Overview of CERN - Discover a world where the impossible is made possible!
At CERN, the European Organization for Nuclear Research, we are pushing the frontiers of science and technology. Our groundbreaking work brings together not only physicists but also a diverse range of professionals from engineering, technical, scientific, and administrative fields. Together, we foster an environment where innovation and collaboration thrive.

Every day, we face exciting new challenges and opportunities to contribute to cutting-edge research that shapes our understanding of the universe. We meet these challenges through the diverse perspectives within our teams, ensuring every contribution is valued and driving our shared sense of inclusion and purpose. Diversity is a core value of CERN since its foundation, and it remains central to our mission and continued success.

If you are ready to be part of a dynamic, inclusive community pushing the boundaries of knowledge, CERN is the place where your curiosity and skills can thrive. Be part of our mission to uncover what lies at the heart of the universe! TAKE PART!
More information about us, here: careers.cern

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