Lukas Fleischer

About Me

Toronto, Canada

Please do not send emails to spmtrp@lfos.de.

lfleischer@lfos.de

A917 6475 9326 B440

I am an entrepreneur and software engineer based in Toronto, passionate about technology that solves real problems and creates meaningful impact. I'm currently focused on building and scaling a profitable SaaS business.

Until the end of 2023, I was a software engineer at Google Canada and

technical lead of Google Cloud's Anti Money Laundering AI machine learning infrastructure team,
inventor and technical lead of a novel patent-pending framework for conducting ML experiments on customer data in a safe and privacy-preserving way,
member of the Cloud AI Data Stewardship committee, managing data governance and compliance for Google Cloud's AI products.

Prior to my time at Google, I was a researcher and post-doctoral fellow

in the Cheriton School of Computer Science, University of Waterloo and
in the Institute for Formal Methods in Computer Science, University of Stuttgart,
conducting research in the following areas: automata theory, formal languages, semigroup theory, algorithms, computational complexity and formal verification.

I am an Arch Linux Developer, Arch Linux Package Maintainer, and active contributor to several other open source projects.

My other areas of interest include financial markets, health/fitness, climate/sustainability, and travel.

Short CV

Oct 2024–today	Entrepreneur, Toronto
Nov 2023–Jun 2025	World trip, South-East Asia and Americas
Dec 2022–Nov 2023	Tech Lead Manager / Senior Software Engineer, Google Canada
Nov 2021–Nov 2022	Senior Software Engineer, Google Canada
Mar 2020–Oct 2021	Software Engineer, Google Canada
May 2019–Dec 2019	Postdoctoral Fellow, School of Computer Science, University of Waterloo
Aug 2015–Feb 2019	Ph.D. Computer Science, FMI, University of Stuttgart
Oct 2013–May 2015	M.Sc. Computer Science, University of Stuttgart
Oct 2010–Nov 2013	B.Sc. Computer Science, University of Stuttgart
Mar 1990	Born, Bietigheim-Bissingen

Research Publications

A list of my publications can also be found on DBLP.

Conference Articles

Lukas Fleischer, Florian Stober, Alexander Thumm, and Armin Weiß. Membership and Conjugacy in Inverse Semigroups. ICALP 2025.
Lukas Fleischer and Jeffrey Shallit. The State Complexity of Lexicographically Smallest Words and Computing Successors. DLT 2020.
Lukas Fleischer and Manfred Kufleitner. Testing Simon's congruence. MFCS 2018.
Lukas Fleischer. The Intersection Problem for Finite Semigroups. DLT 2018.
Lukas Fleischer. On the Complexity of the Cayley Semigroup Membership Problem. CCC 2018.
Lukas Fleischer and Manfred Kufleitner. The Intersection Problem for Finite Monoids. STACS 2018.
Volker Diekert and Lukas Fleischer. Church-Rosser Systems, Codes with Bounded Synchronization Delay and Local Rees Extensions. WORDS 2017.
Lukas Fleischer and Manfred Kufleitner. Green's Relations in Finite Transformation Semigroups. CSR 2017.
Lukas Fleischer and Manfred Kufleitner. Operations on Weakly Recognizing Morphisms. DCFS 2016.
Lukas Fleischer and Manfred Kufleitner. Efficient Algorithms for Morphisms over Omega-Regular Languages. FSTTCS 2015.
Lukas Fleischer, Manfred Kufleitner and Alexander Lauser. Block Products and Nesting Negations in FO². CSR 2014.

Journal Articles

Lukas Fleischer. The Cayley Semigroup Membership Problem. Theory of Computing. 2022.
Lukas Fleischer and Jeffrey Shallit. Automata, Palindromes, and Reversed Subwords. Journal of Automata, Languages and Combinatorics, volume 26, numbers 3–4, pp 221–253. 2021.
Lukas Fleischer and Jeffrey Shallit. Recognizing Lexicographically Smallest Words and Computing Successors in Regular Languages. International Journal of Foundations of Computer Science, volume 32, issue 6, pp 641–662. World Scientific, 2021.
Lukas Fleischer. The Intersection Problem for Finite Semigroups. International Journal of Foundations of Computer Science, volume 31, issue 6, pp 827–842. World Scientific, 2020.
Lukas Fleischer, Samin Riasat, and Jeffrey Shallit. New Bounds on Antipowers in Words. Inf. Proc. Letters, volume 164. 2020.
Lukas Fleischer and Trevor Jack. The Complexity of Properties of Transformation Semigroups. International Journal of Algebra and Computation, volume 30, issue 3, pp 585–606. World Scientific, 2019.
Lukas Fleischer and Manfred Kufleitner. The Complexity of Operations on Weakly Recognizing Morphisms. RAIRO-Theor. Inf. Appl., volume 53, number 1-2, pp 1–17. EDP Sciences, 2018.
Lukas Fleischer and Manfred Kufleitner. Green's Relations in Deterministic Finite Automata. Theory of Computing Systems, volume 63, issue 4, pp 666–687. Springer, 2018.
Lukas Fleischer, Manfred Kufleitner and Alexander Lauser. The Half-Levels of the FO² Alternation Hierarchy. Theory of Computing Systems, volume 61, issue 2, pp 352–370. Springer, 2017.

Unpublished Papers

Lukas Fleischer. Algorithms and Complexity Results for Finite Semigroups. PhD thesis, 2019.
Lukas Fleischer. Efficient Membership Testing for Pseudovarieties of Finite Semigroups. Technical report, 2018.

Open Source Projects

I am an Arch Linux Developer and an Arch Linux Package Maintainer.

I currently maintain roughly 200 packages in the official Arch Linux package repositories.
Between 2011 and 2020, I led the development of the Arch User Repository web interface.
I contributed to other software and tools in the Arch ecosystem, such as the package manager pacman and the Arch Linux devtools.

I am the current maintainer of calcurse, a powerful command-line based calendar program.

I contributed to many other projects in the past, including the version control system Git and the Git web frontend cgit.