Stefan Marr

Associate Professor (Senior Lecturer)
and Royal Society Industry Fellow

Stefan Marr I am working at the School of Computing at the University of Kent. My work focuses on programming language implementation techniques, complex concurrent systems, and tooling.

Much of work revolves around making interpreters faster, detecting and preventing concurrency bugs at run time, and use modern language runtime systems to provide programmers with better tooling.

For contact details see my page at the School of Computing.

Archive of posts with the tag Java

Sep 17, 2024: Instrumentation-based Profiling on JVMs is Broken!

Last year, we looked at how well sampling profilers work on top of the JVM. Unfortunately, they suffer from issues such as safepoint bias and may not correctly attribute observed run time to the correct methods because of the complexities introduced by inlining and other compiler optimizations.
Sep 20, 2023: Don't Blindly Trust Your Java Profiler!

How do we know on what to focus our attention when trying to optimize the performance of a program? I suspect at least some of us will reach for sampling profilers. They keep the direct impact on the program execution low, and collect stack traces every so often during the program execution. This gives us an approximate view of where a program spends its time. Though, this approximation as it turns out can be surprisingly unreliable.
Oct 10, 2022: The Cost of Safety in Java

Overhead of Null Checks, Array Bounds, and Class Cast Exceptions in GraalVM Native Image
Oct 22, 2016: Language Research with Truffle at the SPLASH'16 Conference

Next weekend starts one of the major conferences of the programming languages research community. The conference hosts many events including our Meta’16 workshop on Metaprogramming, SPLASH-I with research and industry talks, the Dynamic Languages Symposium, and the OOPSLA research track.
Sep 17, 2014: Fork/Join Parallelism in the Wild: Documenting Patterns and Anti-Patterns in Java Programs using the Fork/Join Framework

Parallel programming is frequently claimed to be hard and all kind of approaches have been proposed to solve the complexity issues. The Fork/Join programming style introduced with Cilk enables the parallel decomposition of problems in a recursive divide-and-conquer style, and on the surface looks very simple with its minimalistic approach of having a fork and a join language construct. But is it actually simple to use? To find out, Mattias started to dig through the Java open source projects on GitHub and tried to identify common patterns. Next week, he will present our findings at PPPJ’14.