Markus Himmel
Research Software Engineer Tech Lead at Lean FRO
Karlsruhe, Baden-Württemberg, Germany
Summary
🤩
Rockstar🎓
Top SchoolMarkus Himmel is a Research Software Engineer and Tech Lead with 13 years of experience building high-performance algorithms, language tooling, and maintainable software. He currently leads standard library development for Lean, contributing to the Lean 4 theorem prover and refactoring its core to improve performance and correctness. Previously he designed and implemented constraint-optimization engines and Java backends for industrial product configuration at CAS Software AG, and has a strong track record of systems-level contributions to projects like the Haiku OS. Trained in mathematics and computer science at KIT and Cambridge, he brings rigorous formal foundations to practical engineering problems. Markus combines deep theoretical insight (category theory and theorem-proving libraries) with hands-on improvements in performance-sensitive data structures and long-term API and architecture design.
13 years of coding experience
3 years of employment as a software developer
Master of Advanced Study, Pure Mathematics, Merit (equivalent to First Class Honours), Master of Advanced Study, Pure Mathematics, Merit (equivalent to First Class Honours) at University of CambridgeBachelor of Science - BS, Mathematics, 1.0 (best possible), Bachelor of Science - BS, Mathematics, 1.0 (best possible) at Karlsruhe Institute of Technology (KIT)High School, Mathematics and Computer Science, 1.0, High School, Mathematics and Computer Science, 1.0 at Internatsschule Schloss Hansenberg
German, English
Github Skills (20)
c-language10
rtf10
hashmap10
haiku10
kernel10
category-theory10
slim10
theorem-proving10
hash10
t410
cprogramming-language10
operating-system10
proofs9
integer-arithmetic9
proof9
Programming languages (12)
Github contributions (5)
leanprover-community/mathlib3
Feb 2020 - Dec 2022
Lean 3's obsolete mathematical components library: please use mathlib4
Role in this project:
Back-end Developer
Back-end DeveloperContributions:252 reviews, 248 commits, 171 PRs in 2 years 10 months
Contributions summary:Markus's primary contribution appears to be the implementation of foundational category theory concepts, specifically within the category theory library `mathlib3`. The commits show a focus on defining and working with mathematical structures like kernels, coequalizers, and biproducts. Additionally, the user has been actively involved in updating the code, renaming lemmas, and adding specific structures for various mathematical objects. The contributions directly relate to the core mathematical component library's development.
maththeorem-provingcomponents-librarymathematicsjavascript
leanprover/lean4
Jan 2021 - Apr 2025
Lean 4 programming language and theorem prover
Role in this project:Back-end Developer
Back-end DeveloperContributions:403 reviews, 199 PRs, 290 pushes in 4 years 3 months
Contributions summary:Markus contributed to the Lean 4 programming language and theorem prover, primarily by refactoring the codebase. The contributions included moving documentation for syntax from the elaborator to the parser, adding lemmas related to integer arithmetic, and fixing incorrect docstrings for syntax-related features. Furthermore, the user optimized the performance of the HashMap data structure.
dependent-typeshomotopy-type-theoryprovertheoremtheorem-prover
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