Software Engineer – High-Performance Computing

What you'll do

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.

More about Geant4: https://geant4.web.cern.ch/

More about ROOT: https://root.cern.ch/

Learn more

Your responsibilities

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.
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.

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Your profile

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

Your skills

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.
Has a structured and organised approach towards work; is able to set priorities and plan tasks with results in mind.
Finds the information needed to solve problems; makes objective judgements based on all the facts available.
Expresses opinions, ideas and suggestions with conviction and in a logical/structured manner; keeps to the point.
Shares knowledge and expertise freely and willingly with others; coaches others to ensure knowledge transfer.
Adapts quickly and resourcefully to shifting priorities and requirements.
Spoken and written English, with a commitment to learn French.

Ideal start date: 01/11/2026

Contract duration (in months): 60

Grade range: 6

Benchmark job: 200020 - Computing Engineer

Job flexibility: Hybrid

Team supervision

Employment conditions

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

Global Benefits at CERN

A minimum net entry-salary of 9236 Swiss Francs per month, 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.

Let's get you ready

Be sure to meet the eligibility criteria

You are a national of a CERN Member State or Associate Member State. Currently, we cannot consider applications from Pakistani and Lithuanian nationals for positions with a 2026 start date, as the ceiling defined under Article II.5 of the Associate Membership Agreement has been reached.
You have relevant qualifications and professional experience.
If you have previously held a Staff contract at CERN, you will not be eligible for these positions.
Please pay attention to the additional criteria and requirements for this specific position and mentioned above.

You will need these documents to complete your application

Your CV (English or French)
Any document you consider relevant to your application

Your CERNDepartment

The EP department conducts research in experimental particle physics in close collaboration with and supporting the wider scientific community working at CERN. This includes designing and operating experiments, developing and constructing detectors, acquiring and analysing physics data.

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!

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Still have a doubt ? Here are the most frequently asked questions

What should I expect during my first week at CERN?

Your onboarding at CERN includes a comprehensive induction programme, which starts with an official welcome session at the beginning of each month. In addition, you will receive important information both before and after your arrival to ensure a smooth transition into your new role. This process is designed to help you get acquainted with CERN’s environment, your team, and the tools and systems you’ll be using.
How big would the team be?

The size of the team you'll be working with at CERN depends on the specific role and department. Some teams are small and highly specialized, while others are larger and more interdisciplinary. During the interview process, you'll have the opportunity to learn more about the team structure for the position you are applying for.
What is the working language at CERN?

The working languages at CERN are English and French. However, it is not always mandatory to speak both languages to work at CERN. We offer language training to help you acquiring the other language.
What support does CERN provide for relocation?

CERN does not offer direct assistance with relocation. However, depending on your role and specific criteria, you may be eligible for certain benefits such as an installation allowance and coverage of travel expenses to join CERN. These benefits are designed to help ease the transition when relocating to the Geneva area. For more information, please consult the “Salary, Benefits and Support“ page.
Do I need a visa to work at CERN?

Whether you need a visa to work at CERN depends on your nationality and the duration of your stay. CERN assists with the necessary visa and work permit processes for its employees and visitors. The specific requirements will be communicated to you during the recruitment process.
What would my salary be?

Salaries at CERN are determined by a structured scale. Salaries are based on your role, qualifications, and experience, and are not subject to negotiation. Specific details will be provided as your application progresses. For more information, please refer to the dedicated page.