Company Overview
Flux Computing designs and manufactures optical processors to train and run inference on large AI models. Join us in London to be part of a highly motivated and skilled team that thrives on delivering impact and innovation at speed.
The Role
We’re searching for a Performance Modelling Engineer to create and own the analytical and simulation models that steer OTPU architecture and software evolution. You will build functional simulators as well as high-fidelity, cycle-accurate models of our optical compute system. This role is critical to explore “what-if” design spaces, and deliver insights that directly influence our software, hardware, and optical roadmaps. This role sits at the crossroads of hardware architecture, software tooling and machine-learning workload analysis, perfect for an engineer who loves data-driven decision-making and fast iteration.
Responsibilities
* Project Ownership: Own and deliver projects on your team's roadmap that unlock key high-impact technical and business milestones that drive the success of Flux.
* Collaboration: Work shoulder-to-shoulder with hardware, compiler and ML framework teams to ensure models reflect reality and reality meets performance goals.
* Functional Simulator: Design, build, and maintain a functional simulator of the OPTU subsystem and full pipeline.
* Performance Simulator: Design and maintain architectural & cycle-accurate models of the OPTU subsystems and pipeline. Identify throughput, latency and utilisation hot-spots; propose architectural, or scheduling fixes.
* Workload Analysis & Bottleneck Hunting: Instrument benchmarks (LLMs, diffusion, graph workloads) to collect detailed traces.
* Design-Space Exploration: Run massive parameter sweeps with your functional and to understand tradeoffs and guide the software, hardware, and optical teams. Package results into clear, quantitative analyses and design recommendations.
* Tooling & Automation: Develop Python/C++ tooling for trace parsing, statistical analysis and visualisation. Integrate models into CI so that every RTL commit gets a performance smoke test.
Skills & Experience
* 5+ years building performance or power models for CPUs, GPUs, ASICs, or accelerators
* Strong coding ability in C++ and Python; experience with discrete-event or cycle-accurate simulators (e.g., gem5, SystemC, custom in-house).
* Solid grasp of computer-architecture fundamentals: memory systems, interconnects, queuing theory, Amdahl/Gustafson analysis.
* Familiarity with machine-learning workloads and common frameworks (PyTorch, TensorFlow, JAX).
* Comfort reading RTL or schematics and discussing micro-architectural trade-offs with hardware designers.
* Excellent data-visualisation and communication skills: able to turn millions of simulation samples into one decisive slide.
* Bachelor’s+ in EE, CS, Physics, Applied Maths or related; advanced degree preferred but not required.
* Personal or open-source projects in simulators, ML kernels, or performance analysis are a significant plus.
Compensation & Benefits
* Competitive salary and stock options in a rapidly growing AI company.
* Based in our new 5,000 sq. ft. office in the AI hub of Kings Cross, London.
* To foster collaboration in our high-growth environment, we require all employees to work from our London HQ and live within a 45-minute commute. We offer an extra £24,000/year incentive for those living within 20 minutes.
* Comprehensive healthcare insurance.
* 25 days PTO policy plus bank holidays.
* Private access to our in-house 3D printer.
If you are passionate about pushing the boundaries of what's possible in AI and thrive in a high-energy, fast-paced environment, we want to hear from you. Apply now to join Flux and be a key player in shaping the future of computing.