Research

My publications are listed on the publications page.

Current Projects

• GraalVM, Native Image, and Truffle (since 2025, funded by Oracle)
  We are collaborating with Oracle to bring the GraalVM to new use cases, which means we work on improving the performance of the systems with a focus on compilation, interpretation, and garbage collection.
• INDIMO: Invariant Discovery and Monitoring for Message-Passing Programs (2026–2029, funded by EPSRC)
  Software will always have properties that can't be proven statically. But, perhaps we can prove more properties by using details we learn at runtime.
  
  
• Building Faster Languages Faster! (since 2013)
  Writing custom VMs for DSLs or research languages is not practical.
  So, how can we reuse JIT compilers for new languages?
  • AST vs. Bytecode: Interpreters in the Age of Meta-Compilation
  • Add Graal JIT Compilation to Your JVM Language in 5 Easy Steps, a Tutorial
  • Tracing vs. Partial Evaluation
  • Zero-Overhead Metaprogramming
  
  
• SOM: Simple Object Machine (maintainer since 2012)
  A simple Smalltalk for teaching and experimenting with language implementation techniques. Implemented among others in Java, C, C++, Smalltalk, and Python.
  Current highlights:
  • SOM++
    SOM++ used by IBM to showcase Project OMR's GC and JIT compiler
  • TruffleSOM
    SOM implemented based on Oracle's GraalVM.
  • PySOM
    SOM implemented with RPython, similar to TruffleSOM, showcasing the power of self-optimizing interpreters.
  
  

Previous Projects

• Automatic Superinstructions for Bytecode Interpreters (2024, funded by Oracle Labs)
  Metacompilation systems currently have high interpreter overheads. In this project, we will explore ways to reduce the overhead of bytecode interpretation.
• Royal Society Industry Fellowship: FastStart: Fast Single Truth Language Runtimes (2021–2024, funded by The Royal Society)
  Turns out a lot of programs spent a lot of time in interpreters, instead of compiled code. In this project, we explore how we can reduce the semantic duplication in language implementations, while at the same time, improving interpreter performance.
  
  As Industry Fellowship, this project is in collaboration with Shopify
  
  
  
• Project CaMELot: Catching and Mitigating Event-Loop Concurrency Issues (2021–2024, funded by EPSRC)
  The pessimistic view is that programs will always have bugs. The optimistic one is that we can teach our runtime systems to detect them and automatically prevent them from causing problems.
  
  
• Safely Combining Concurrency Abstractions (2012–2024)
  Concurrent programming is hard, and we make it harder by using abstractions that cannot be combined safely.
  In this project, we search for safe and efficient combinations.
  • SOMns, a fast Newspeak as platform for concurrency research
  • Why is Concurrent Programming hard? And What Can We do About It?
  
  
• Meta-Level Engineering and Tooling for Complex Concurrent Systems (2016–2021)
  In this project, we work on instrumentation and tooling for applications that combine concurrency abstractions.
  Partners: Vrije Universiteit Brussel, Johannes Kepler University Linz
  
  
• OMOP: Supporting Concurrency Abstractions in Virtual Machines (2008–2013)
  An Ownership-based Metaobject Protocol to support concurrent programming in multi-language VMs
  
  
• Project Renaissance: Harness Emergence (2009–2011)
  Avoid the Concurrency Trap by Embracing Non-Determinism.
  Partners: IBM Research, Portland State University, and Vrije Universiteit Brussel

PhD Student Guidance, Mentoring, Collaboration

As Primary Supervisor

19. Christoph Aigner, since 2025
20. Thomas Schrott, since 2025
21. Florian Huemer, since 2025
22. Christoph Pichler, 2025–2026
23. Humphrey Burchell, 2022–2026
24. Octave Larose, 2021–2026
25. Sophie Kaleba, 2019–2025

As Part of the Supervisory Team

12. Joel Jakubovic, 2019–2023
13. Javier Pimás, 2016–2024
14. Dominik Aumayr, 2017–2021
15. Carmen Torres López, 2016–2021
16. Benoit Daloze, 2015–2019
17. Guido Chari, 2014–2017
18. Clément Béra, 2014–2015
19. Camillo Bruni, 2014
20. Janwillem Swalens, 2013–2015
21. Thierry Renaux, 2012–2015
22. Mattias De Wael, 2011–2015
23. Joeri De Koster, 2009–2015

Academic Services

Organization

• Conference Program Committee Chair: DLS'23 MPLR'20, DLS'19, and <Programming>'19
• Steering Committees: MPLR (since 2019), DLS (since 2019), ICOOOLPS (since 2019), <Programming> (since 2019), VMIL (since 2018), MoreVMs (since 2017), SPLASH (2023, as observer)
• Workshop Organizer: MoreVMs 2017–2019, 2023, 2024, VMIL'18, Meta 2016–2018, ICOOOLPS'16, Reflect'16, SCRIPT'13
• PLDI Workshops & Tutorials Co-Chair 2020, 2021
• Workshops & Tutorials Co-Chair for <Programming> 2018, 2019
• Web Chair for ECOOP'19

Reviewing

• Program Committee Member of Conferences: OOPSLA'25, <Programming>'25, ISMM'24, <Programming>'24, SLE'23, ICPP'23, OOPSLA'22, SLE'22, ESOP'22, ISMM'21, ICPP'21, <Programming>'19, Onward!'18, GPCE'18, DLS'18, ICPP'18, ICPP'17, VEE'17, DLS'14
• Member of the external review committee of ECOOP'25, OOPSLA'20
• Program Committee Member of other events: DEBT'25, DEBT'23, Erlang'22, CoDoCo'21, AGERE'19, PLACES'19, COP'18, PX/18, PX/19, SPLASH'17 Workshops, COP'17, PASS'17, OOPSLA AEC'17, VMM'17, ICOOOLPS'17, SPLASH'16 Workshops, VMM'16, CROW'16, AGERE'15, ECOOP AEC'15, ICOOOLPS'14, RACES'12, MISS.12, MISS.11, VMIL'09
• ACM Student Research Competition at SPLASH'18, <Programming>'17
• Sub-Reviewer: OOPSLA'13, ECOOP'13, Coordination'13, TOOLS'11, AOSD'10, Coordination'10, DLS'10, ECOOP'10, OOPSLA'10, AOSD'09, DLS'09
• Journal Reviewing:
  Journal of Object Technology (JOT),
  ACM Transactions on Programming Languages and Systems (TOPLAS)
  The Programming Journal: The Art, Science, and Engineering of Programming
  ACM Computing Surveys
  The Computer Journal
  Journal on Computer Languages, Systems and Structures
  Journal of Computational Science
  IEEE Access
  Journal of Systems and Software
  Journal of Science of Computer Programming
  Journal of Logical and Algebraic Methods in Programming
  Journal of Parallel Computing
• Grant Reviewing:
  EPSRC, Invited Member of Peer Review College (since 2024)
  DFG, German Research Foundation
  EPSRC, Engineering and Physical Sciences Research Council
  NSERC, Natural Sciences and Engineering Research Council of Canada
  NWO, The Dutch Research Council

Latest Research-Related Posts

• Aug 20, 2026 Pitfalls of Benchmarking on Modern Systems
• Jun 16, 2026 SSW@ECOOP'26: On Debugging, Benchmarking and (Meta-)Compilation
• Jan 20, 2026 Python, Is It Being Killed by Incremental Improvements?
• Nov 17, 2025 Benchmarking Language Implementations: Am I doing it right? Get Early Feedback!
• Oct 15, 2025 Can We Know Whether a Profiler is Accurate?
• Aug 27, 2025 How to Slow Down a Program? And Why it Can Be Useful.
• Sep 17, 2024 Instrumentation-based Profiling on JVMs is Broken!
• Jun 18, 2024 5 Reasons Why Box Plots are the Better Default Choice for Visualizing Performance
• Feb 23, 2024 Why Are My Bytecode Interpreters Slow? Hunting Truffles with VTune
• Feb 13, 2024 Rank 10 Language Implementations

All posts: Research