Thursday, October 21, 2010

OOPSLA day 1 (JOT repost)

OOPSLA proper starts today. William Cook gave a mercifully short introduction and then we were straight into the first ever SPLASH invited talk, on evolving software by Stephanie Forrest. After the break, I attended the Onward! research paper stream, then after lunch an OOPSLA session, and the panel in the last session.

Registration-Based Language Abstractions - Samuel Davis

Samuel presented a method for adding language constructs to a language. These constructs are outside of the language, but also outside of the source code, so each programmer can have their own personal version of a programming language and the tool will present code using the right constructs. It seems like a very sophisticated macro system to me, but with better tool support (I don't mean this in a derogatory way, the system is obviously more powerful and useful than macros, I just mean it as a simile).

I attended, enjoyed and found interesting two talks - Pinocchio: Bringing Reflection to Life with First-class Interpreters presented by Toon Verwaest, and Lime: A Java-Compatible and Synthesizable Language for Heterogeneous Architectures presented by Joshua Auerbach. I'm afraid I can't say much about either of them, but they were good talks and I'll try to read both papers.

From OO to FPGA: Fitting Round Objects into Square Hardware? - Jens Palsberg

A talk on compiling high-level languages to FPGAs, the challenge is to compile a standard OO program to an FPGA. Currently code written in a small subset of C can be compiled to FPGAs, but hand-coded FPGA code is better (faster, less area, smaller energy consumption). The general technique presented is to compile from Virgil to C and then to FPGAs. Unfortunately, the C subset is so small (no pointers, etc.) that objects cannot be compiled in the usual way.

The authors used a mix of existing compilation techniques with some new ideas of their own. Essentially they compile objects to sparse integer arrays, but must then expend a lot of effort in compressing these tables.

They have experimental results which show slightly better performance for their tool chain than for the hand-tuned version (for the non-oo case). In the OO case, it is harder to compare (no-one else has done it), but by interpreting performance results from CPU execution, they reason that their tool gives good results here too.

An interesting challenge which emerged in the questions, is producing an intermediate language for compilation to FPGAs that preserves parallelisation, as opposed to C which 'flattens' away any parallel code into sequential code.

Panel - Manifesto: a New Educational Programming Language

For the last session of the day, I attended the panel session on a proposed new programming language, aimed at first year university students. The language is called Grace (, it is proposed to be a community effort, with a semi-open development process and this panel was an effort to get the community behind it. Grace will be a general purpose (as opposed to domain specific) language, designed for novices (so no fancy type system), and deigned for programming in the small (so no fancy module system). It will not be industrial strength, therefore it will not need to be backward compatible, and should have low overhead for small programs (no "public static void main").

The proposers argued that the time is right: Java will be good for the next few years, but is getting big and a bit long in the tooth. Alex Buckley (Java "theologist", also on the panel, but not associated with Grace) did not disagree, but did say that Java would have a lot of the features discussed in a few years time (which means it might not look so old but will be even bigger).

The proposers (James Noble, Andrew Black, and Kim Bruce) have ambitious goals: Grace should be multi-platform, multi-paradigm (it should support teaching with or without objects, with or without types, in a functional or procedural style), it should be useful for teaching first and second years how to program, and for data structures courses. With Smalltalk never far below the surface, it was declared that everything would be an object, although it was not stated what was meant by "everything". The proposers proposed that Grace have a powerful extension/library system for adding in things like concurrency, basically because we don't know the best way to do concurrency right now. This seems a big ask, one thing the concurrency community mostly agress on is that concurrency cannot be added on afterwards, it must be holistically baked in.

It sounds to me like a great idea - an academic, community based teaching language should be much better suited for purpose than a professional programming language. But, to be honest, the session did not have very much buzz. The panel itself was obviously excited about the project, the audience less so. There were no great questions from the floor, or any really exciting debate. The lengthiest discussion was about the relative merits of the PLT group's book/language/curriculumn. On the other hand no one really disagreed that there was a gap in the market for such a language. I'm interested to find out if the proposers got encouraging words after the session. (Disclaimer: I skipped the last half hour to attend a research talk, so the session might have lit up then and I would have missed it.)

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