Apr 17, 2015 - Speaking at jsconf.be on "The Road to ES6, and Beyond"


Next week I will be speaking at jsconf.be in lovely Bruges, Belgium. It’s the second edition of the local Belgian JavaScript community gathering and it’s promising to be quite an interesting program with talks on some of the usual suspects: React, Angular, Meteor, node and some less usual suspects, like the Cody CMS, a content-management system written 100% in JS. Perhaps unsurprisingly given recent events, I will be speaking about ECMAScript 6, which is nearing completion (at the time of writing, TC39 itself has signed off on the spec, but it is pending formal approval from ECMA). This is quite a historical moment. As Allen Wirfs-Brock, the editor of the ES6 spec put in the foreword of the new spec:

Focused development of the sixth edition started in 2009, as the fifth edition was being prepared for publication. However, this was preceded by significant experimentation and language enhancement design efforts dating to the publication of the third edition in 1999. In a very real sense, the completion of the sixth edition is the culmination of a fifteen year effort.

The title of my talk at jsconf.be is “The Road to ES6, and Beyond”. It’ll be about three things:

  • Part I: JavaScript’s past, and the long road to ECMAScript 6: I’ll give some background on the history of JavaScript, what “ECMAScript” is all about, who TC39 is and what they do. I’ll also recount the “harmony”-era decision that led first to a general cleanup of the language (ES5 strict mode) which then paved the way for growing the language, culminating in the ES6 effort.
  • Part II: a brief tour of ECMAScript 6: this is the part most probably of interest to JS devs. I’ll give an overview of some of the more significant new language features in ES6. It’s difficult to be exhaustive here, so I’ve focused mainly on the many improvements to functions, the addition of classes and modules, and new control flow abstractions like iterators, generators and promises.
  • Part III: using ECMAScript 6 today, and what lies beyond: this part will be on the practical issue of writing ES6 code in a time where none of the major platforms have yet fully implemented the spec. I’ll discuss some ES6-to-ES5 compilers like Traceur, BabelJS and TypeScript (yes, I’m aware the latter is not technically an ES6 compiler, but it’s a relevant tool in this space). I’ll end with an outlook on what’s on the table for ES7 (or I should say, ECMAScript 2016), focusing on some of the more mature features.

I consider it a privilege to be given the chance to talk to the JS community about these exciting new features. The timing couldn’t be better.

Update: slides of my talk. If you’re interested in me giving this talk at your company or event, do get in touch.

Jul 16, 2014 - Java Fork/Join Parallelism in the Wild


My student Mattias De Wael, with guidance from Stefan Marr and myself, recently published a study on how the Java Fork/Join framework is being used in practice by developers. From the abstract:

The Fork/Join framework […] is part of the standard Java platform since version 7. Fork/Join is a high-level parallel programming model advocated to make parallelizing recursive divide-and-conquer algorithms particularly easy. While, in theory, Fork/Join is a simple and effective technique to expose parallelism in applications, it has not been investigated before whether and how the technique is applied in practice. We therefore performed an empirical study on a corpus of 120 open source Java projects that use the framework for roughly 362 different tasks. On the one hand, we confirm the frequent use of four best-practice patterns (from Doug Lea’s book) – Sequential Cutoff, Linked Subtasks, Leaf Tasks, and avoiding unnecessary forking – in actual projects. On the other hand, we also discovered three recurring anti-patterns that potentially limit parallel performance: sub-optimal use of Java collections when splitting tasks into subtasks as well as when merging the results of subtasks, and finally the inappropriate sharing of resources between tasks.

To me, the most interesting outcome was the observation that the Fork/Join API could benefit from the Java Collections API being extended with collections that can be efficiently split and merged. Often, developers choose suboptimal data structures, or suboptimal methods on existing data structures to do recursive splits/merges. Although perhaps that isn’t even necessary, as it turns out Java 8 Streams effectively cover typical use cases of Fork/Join such as parallel maps and reduces, without the developer having to manually split and merge the collection anymore. The paper has been accepted at PPPJ 2014. The original submission can be accessed here.

May 21, 2014 - AmbientTalk actors are data race and deadlock free


We recently published a new article on AmbientTalk, an actor language I co-designed with a focus on developing mobile applications for ad hoc wireless networks. The main novelty of the article is what we believe to be the first formal account of the communicating event loops model, which is the concurrency model underlying the family of actor languages upon which AmbientTalk is based. Interestingly, this model is also closest to the concurrency model you get in JavaScript, if you think of a WebWorker as an actor. The article gives a comprehensive overview of AmbientTalk’s roots, the language itself, and introduces a “featherweight AmbientTalk” calculus with an operational semantics. We use it to establish data race freedom (actors have isolated memory) and deadlock freedom (assuming all event loop turns are finite, all asynchronous messages sent between actors will eventually be processed). The article is published in the journal “Computer Languages, Systems & Structures”. A preprint copy of the paper is available here. Quoting the abstract:

The rise of mobile computing platforms has given rise to a new class of applications: mobile applications that interact with peer applications running on neighbouring phones. Developing such applications is challenging because of problems inherent to concurrent and distributed programming, and because of problems inherent to mobile networks, such as the fact that wireless network connectivity is often intermittent, and the lack of centralized infrastructure to coordinate the peers. We present AmbientTalk, a distributed programming language designed specifically to develop mobile peer-to-peer applications. AmbientTalk aims to make it easy to develop mobile applications that are resilient to network failures by design. We describe the language’s concurrency and distribution model in detail, as it lies at the heart of AmbientTalk’s support for responsive, resilient application development. The model is based on communicating event loops, itself a descendant of the actor model. We contribute a small-step operational semantics for this model and use it to establish data race and deadlock freedom.

Feb 5, 2014 - Moving to Bell Labs

As of this month, I’m working for Alcatel-Lucent Bell Labs in Antwerp, Belgium. I will be doing distributed systems research with a focus on programmability and programming models. I’m still active part-time at the VUB Software Languages Lab.

Jul 4, 2013 - Direct Proxies talk at ECOOP

Yesterday I gave a talk at the European Conference on Object-oriented Programming (ECOOP) on our paper on direct proxies in JavaScript. The slides are available online. The talk is basically recounting the story of how Mark and I refactored the original JavaScript Proxy API into the current direct proxies API because of the interaction between proxies and frozen objects. I have previously written about that interaction on my blog. The paper further focuses on membranes as a case study for proxies.