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December 2017
ESOP paper accepted! Correctness of a fully concurrent Garbage Collector for Actor Languages,
by Juliana Franco, Sylvan Clebsch, Sophia Drossopoulou, Jan Vitek and myself has been accepted for ESOP 2018.
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November 2017
SAC OOPS paper accepted! OOLONG — An Extensible Concurrent Object Calculus,
by my soon-to-finish PhD student Elias Castegren and myself. The OOLONG calculus is a small,
extensible calculus fully formalised in Coq. If you want to model stateful object-oriented
languages, then OOLONG might be your cup of tea! A link to the finished paper, Coq sources,
LaTeX sources, and OTT definitions will appear here soon.
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November 2017 On November 29th, I'm organising the
11th multicore day as part of the SICS software week. The line-up for this year is great (here in lexicographical order):
- Alberto Ros (U. Murcia) talking about cache coherence protocols of the future
- Claes Redestad (Oracle) talking Java 9 on parallel hardware
- Felix Mulder (Klarna) talking about Scala on parallel hardware and Scala 3
- Georgi Gaydadjiev (Maxeller) talking about the streaming dataflow paradigm
- Kostis Sagonas and Bengt Jonsson (Uppsala U.) talking about testing of concurrent software
- Niko Matsakis (Mozilla) talking about Rust
- Sylvan Clebsch (Microsoft Research) talking about parallel runtimes
- ...and Johan Gronqvist (ARM), Per Stenström (Chalmers) and Davide Rossi (U. Bologna) in a heated panel debate.
Participation is free of charge, but registration is mandatory. First come, first serve!
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October 2017 Action shots from SPLASH'17.
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October 2017 I'm travelling 22/10—28/10 to attend SPLASH'17 and co-located
events in Vancouver, Canada. The week's schedule is quite busy, so expect additional latency in communication.
On Monday, I have
a SPLASH-E paper
with Elias on the course in Imperative and Object-Oriented
Programming that I am currently teaching. On Tuesday, Elias and I have a paper on his capabilities' work at
the OCAP workshop. On Thursday, we are presenting the ORCA paper
on fully concurrent garbage collection at OOPSLA. On
Friday, we are presenting the SHAPES work on efficient abstract data layout for OOP
at ONWARD!.
There is also the NOOL workshop on new object-oriented languages
run by Roly Perera that you should check out if you are attending SPLASH.
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September 2017
OCAP workshop paper accepted: Reference Capabilities for Concurrency & Scalability: an Experience Report,
which surveys the work on reference capabilites by my soon-to-finish PhD student Elias Castegren and myself
will be presented at the inaugural OCAP: Object-Capability Languages, Systems, and Applications,
co-located with SPLASH 2017 in Vancouver.
September 2017 (Shameless plug)
My PhD student Elias Castegren kicked off his “marketing tour” — looking for a PostDoc position
as he is due to finish in the next few months. Here he is giving a talk at the Royal Institute of Technology.
Elias' research interests are programming languages, compilers, type systems, concurrent and parallel programming, object-oriented programming, functional programming and CS education. He is the number one committer (out of 6 core committers) to the Encore programming language, which is implemented in Haskell and C.
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August 2017
SPLASH-E paper accepted! Right on time for (as in same day of) the start of my big
course on Imperative and Object-Oriented Programming Methodology,
the paper on the design of this course (co-authored with Elias Castegren,
who is the head TA for this course for several years) was accepted for SPLASH-E.
If you are a student on this course, you should read the paper to understand
the course's design! As soon as the paper is ready, it will be linked here.
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August 2017
OOPSLA paper on garbage collection accepted: Orca: Leveraging Types and Messaging for Fully Concurrent GC,
joint with Sylvan Clebsch (Microsoft Research Cambridge),
Juliana Franco and Sophia Drossopoulou (Imperial College),
Albert Mingkun Yang (Uppsala University — my PhD student) and
Jan Vitek (Northeastern).
This paper describes the ORCA GC protocol that is used in Pony and Encore, and
explains ORCA's implementation in the Pony run-time.
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August 2017
NOOL 2017 has a CFP out! NOOL is a workshop for
researchers and developers of new object-oriented languages that
is co-located with OOPSLA.
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July 2017
I will be serving on the Programme Committee for PLDI --
Programming Languages Design and Implementation in 2018.
PLDI is the premier forum in the field of programming languages and programming systems research,
covering the areas of design, implementation, theory, applications, and performance.
The acceptance rate of PLDI 2017 was 14,9% (47/314).
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July 2017
I will be serving on the Programme Committee for OOPSLA --
Object-Oriented Programming, Systems, Languages and Applications at
SPLASH in 2018.
OOPSLA seeks outstanding contributions on all aspects of programming languages and software engineering.
Accepted papers will appear in Proceedings of the ACM on Programming Languages (PACMPL),
a Gold Open Access journal.
The acceptance rate of OOPSLA 2016 was 25,6% (52/203).
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July 2017
Onward! paper accepted: Juliana's paper (joint with myself, Sophia Drossopoulou, Susan Eisenbach and Martin Hagelin) You Can Have it All: Abstraction and Good Cache Performance
has been accepted to Onward!.
Camera-ready version forthcoming.
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June 2017
During the AITO General Assembly Meeting held during
ECOOP 2017, I was elected onto the AITO Executive Board
as vice president. This means that I will be more involved in the organisation of future
ECOOPs (I organised ECOOP 2014 in Uppsala).
ECOOP 2017 was a great conference with many great talks, good networking, and a lot of
excellent student activities, including mentoring breakfasts and a summer school.
Please encourage your students to go to ECOOP 2018 in Amsterdam!
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June 2017
The first team of bachelor students just held their presentations.
Six good talks, and several new features being added to Encore.
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June 2017
The team is attending ECOOP+PLDI 2017 at force!
- Albert is presenting his
paper on garbage collection on Sunday 19/6
- Stephan is doing an invited demo of his Spencer tool for interactive dynamic heap analysis
IWACO on Monday 20/6.
You can see his slides here.
- Elias is presenting his
paper on typing lock-free programming on Friday 24/6 and
organising IWACO together with Juliana Franco.
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May 2017
I will be speaking at the PLISS Summer school (Programming Language Implementation Summer School) about Encore in general and about lock-freedom and garbage collection in particular. My talk will cover work with Thorbiörn Fritzon (at Spotify — presented at last NOOL), Elias Castegren (UU — to appear at ECOOP) and Albert Yang (UU — to appear at ISMM).
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April 2017 Next
issue of ACM XDRS will feature
a gender equality event co-organised by
Albert (my PhD student) and Kiko (whom I
co-advice with Dave Clarke). The event was
organised by the local ACM-W chapter in Uppsala
where Kiko is co-chair and Albert is secretary
and treasurer. Hats off to all organisers for
making this happen!
The event brought experts from the IT industry,
who were paired with a group of 3 to 4 students,
and worked together for a day in a project. By
signing up female experts, students experience
(first hand) that females working in IT can also
be leaders, challenging the idea that only men
can be leaders and making a statement female
role models exists.
I am happy for whatever little inching in the right direction.
When I was running advanced education for a big,
international telecommunications company, we talked a
lot about diversity in the work-place. In these classes
I ran into “lots” of (%-age-wise) women who had
trouble not being “promoted out of” the
programming jobs they loved because it was just
assumed that they, as women, would prefer to work
in communication-oriented roles, like non-technical
project management etc., rather than hack.
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April 2017
Elias' paper Relaxed Linear References for Lock-free Data Structures
has been accepted to the European Conference on Object-Oriented Programming.
Camera-ready version forthcoming.
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April 2017
I am happy to announce that my PhD student
Albert will be doing an
internship with the Google V8 team working on garbage collection.
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April 2017
Albert's paper Type-Assisted Automatic Garbage Collection for Lock-Free Data Structures
has been accepted to the 2017 ACM SIGPLAN International Symposium on Memory Management (ISMM). in conjunction with PLDI and ECOOP.
Camera-ready version forthcoming.
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April 2017
I am happy to announce that I have been voted the teacher of the year 2017 by the currently enrolled
CS bachelor and IT Civil Engineering students. The motivation is (translated from Swedish):
For teaching the subject in a pedagogic way, and with
great dedication, the prize goes to Tobias Wrigstad.
As a teacher, he listens to student criticism and
feedback. The teacher has a good standing with the
students, uses an activating means of teaching, and
most importantly is passionate about his subject.
Here are pictures of me accepting the prize together with Elias, my head TA on the IOOPM course,
and some of the TAs of the course installation of 2016.
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March 2017
Stephan's paper Spencer: Interactive Heap Analysis for the Masses
will appear at 14th Conference on Mining Software Repositories in conjunction with ICSE.
Camera-ready version forthcoming. Preprint.
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March 2017
Stephan's paper Mining for Safety using Interactive Trace Analysis
will appear at QAPL 2017 in conjunction with ETAPS.
Camera-ready version forthcoming. Preprint.
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March 2017
Elias' paper Actors without Borders: Amnesty for Imprisoned State
will appear at PLACES 2017 in conjunction with ETAPS.
Workshop version.
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January 2017
Teaching semester ended! The course on Imperative and Object-Oriented Programming Methodology,
got really good reviews from students (as last year!). You can read the course report.
The UPMARC centre of excellence on programming for multicore architectures funded Johan Östlund,
who recently graduated. Johan developed the actor-based language Joelle, among the first actor languages
to use types to achieve isolation, and lifted a single thread of control abstraction for actors in a
data-race free way. Johan graduated in January 2016. UPMARC also funds 
The Structured Aliasing project searches for a theory and practise of structured aliasing to
lift alias management over low-level operations such as assigning individual references to objects
and maintain encapsulation on a per-reference basis, and let programmers create and maintain object
graphs and express alias properties in their programs in an explicated, clear and enforceable way.
[Funded by: Swedish Research Council]
The 
The Thorn project developed a dynamically-typed concurrent language in which lightweight isolated processes communicated by message passing.
This was a joint project between IBM Research and Purdue University.
Thorn was also a playground for like types, a form of gradual types, which are based in nominal types (for programmer understanding),
and strikes a good balance between performance and flexibility.
