SOM, the Simple Object Machine, is a little dynamic language designed for teaching object-oriented virtual machine design. It originates in Aarhus, Denmark, and according to Lars Bak, it was implemented in the course of two days by Kasper Lund. They used it back in 2001 for a course at the University of Aarhus.
Debugging concurrent systems is pretty hard, and we worked already for a while to make things a bit better. However, a big remaining problem is that bugs are not easily reproduced.
Programming languages naturally come with a library of containers or collection types. They allow us to easily work with arbitrary number of elements, which is something all major languages care about. Unfortunately, it seems like there is not much writing on how to design such libraries. Even asking a few people that worked for a long time on collection libraries did not yield much of a structured approach to such a central element for our languages. The one major piece of writing we found is the Scala people describing their experience with bit rot and how they redesigned their collection implementation to avoid it.
When we have to debug applications that use concurrency, perhaps written in Java, all we get from the debugger is a list of threads, perhaps some information about held locks, and the ability to step through each thread separately.
Since SOMns is a pure research project, we aren’t usually doing releases for SOMns yet. However, we added many different concurrency abstractions since December and have plans for bigger changes. So, it seems like a good time to wrap up another step, and get it into a somewhat stable shape.
One possible way for modeling concurrent systems is Tony Hoare’s classic approach of having isolated processes communicate via channels, which is called Communicating Sequential Processes (CSP). Today, we see the approach used for instance in Go and Clojure.
With the Truffle language implementation framework, we got a powerful foundation for implementing languages as simple interpreters. In combination with the Graal compiler, Truffle interpreters execute their programs as very efficient native code.
Now that we got just-in-time compilation essentially “for free”, can we get IDE integration for our Truffle languages as well?
Continuing a little bit with writing notes on Truffle and Graal, this one is based on my observations in SOMns and changes to its message dispatch mechanism. Specifically, I refactored the main message dispatch chain in SOMns. As in Self and Newspeak, all interactions with objects are message sends. Thus, field access and method invocation is essentially the same. This means that message sending is a key to good performance.
The past few month, I have been busy implementing a fast actor language for the JVM. The language is essentially Newspeak with a smaller class library and without proving access to the underlying platform, which can lead to violations of the language’s guarantees.