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 PyPy

Nov 17, 2023: The Changing “Guarantees” Given by Python's Global Interpreter Lock

In this blog post, I will look into the implementation details of CPython’s Global Interpreter Lock (GIL) and how they changed between Python 3.9 and the current development branch that will become Python 3.13.
Apr 28, 2015: Zero-Overhead Metaprogramming

Runtime metaprogramming and reflection are slow. That’s a common wisdom. Unfortunately. Using refection for instance with Java’s reflection API, its dynamic proxies, Ruby’s #send or #method_missing, PHP’s magic methods such as __call, Python’s __getattr__, C#’s DynamicObjects, or really any metaprogramming abstraction in modern languages unfortunately comes at a price. The fewest language implementations optimize these operations. For instance, on Java’s HotSpot VM, reflective method invocation and dynamic proxies have an overhead of 6-7x compared to direct operations.
Sep 22, 2014: Are We There Yet? Simple Language-Implementation Techniques for the 21st Century

The first results of my experiments with self-optimizing interpreters was finally published in IEEE Software. It is a brief and very high-level comparison of the Truffle approach with a classic bytecode-based interpreter on top of RPython. If you aren’t familiar with either of these approaches, the article is hopefully a good starting point. The experiments described in it use SOM, a simple Smalltalk.
Feb 1, 2014: How to get a JIT Compiler for Free: Implementing SOM Smalltalk with RPython and Truffle

Today at FOSDEM, I gave a brief talk on implementing SOM, a little Smalltalk, with RPython and Truffle. RPython, probably best known for the PyPy implementation, uses meta-tracing JIT compilation to make simple interpreters fast. Truffle, a research project of Oracle Lab, is an approach for building self-optimizing interpreters and in combination with Graal, it gives a JIT compiler for AST-like interpreters. In the talk, I briefly sketch both of them, without going into many details.