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Fwd: Séminaire DIRO 24 avril: Harry Mairson
by Marc Feeley 21 Avr '08

21 Avr '08

Hello MSLUGers! This thursday the DIRO is happy to get the visit of Harry Mairson who will be giving a presentation on Control Flow Analysis (CFA). So if you ever wanted to know about advanced Scheme (or Haskell, or any language actually) compiler optimization, this is your chance. Below are the details. Marc Begin forwarded message: > From: Pierre McKenzie <mckenzie(a)iro.umontreal.ca> > Date: April 17, 2008 3:03:36 PM GMT-04:00 > To: seminaires(a)iro.umontreal.ca > Subject: Séminaire DIRO 24 avril: Harry Mairson > > Cordiale bienvenue au prochain séminaire du DIRO! > http://www.iro.umontreal.ca/~mckenzie/ColloquesDIRO/H2008 > > CONFÉRENCIER: Harry Mairson, Brandeis University > TITRE: Linear Logic and the Complexity of Control Flow Analysis > > QUAND: le jeudi 24 avril à 15:30 > OÙ: salle (*attention*) 3195, pavillon André-Aisenstadt, U de Montréal > > RÉSUMÉ: Control flow analysis (CFA) is a kind of static program > analysis performed by compilers, where the answers to questions like > "can call site X ever call procedure P?" or "can procedure P ever be > called with argument A?" can be used to optimize code output by the > compiler. Such questions can be answered exactly by Girard's > geometry of interaction (GoI), but in the interest of efficiency and > time-bounded computation, control flow analysis computes a crude > approximation to GoI, possibly including false positives. > > Different versions of CFA are parameterized by their sensitivity to > calling contexts, as represented by a contour--- a sequence of k > labels representing these contexts, analogous to Lévy's labelled > lambda calculus. CFA with larger contours is designed to make the > approximation more precise. A naive calculation shows that 0CFA > (i.e., with k=0) can be solved in polynomial time, and kCFA (k>0, a > constant) can be solved in exponential time. We show that these > bounds are tight, namely, that the decision problem for 0CFA is > PTIME-hard, and for kCFA is EXPTIME-hard. Each proof depends on > fundamental insights about the linearity of programs. In both the > linear and nonlinear case, contrasting simulations of the linear > logic exponential are used in the analysis. The key idea is to take > the approximation mechanism inherent in CFA, and exploit its > crudeness to do real computation. > > This is joint work with David Van Horn (Brandeis University). > > POUR INFORMATION: Marc Feeley, DIRO.

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Web site down...
by schemeway＠sympatico.ca 17 Avr '08

17 Avr '08

Hi all! As some of you may have noticed, the MSLUG web site is unreachable. The hard disk of my Linux server crashed two days ago and I'm not sure I will be able to install a new one anytime soon... I have a backup of the site, but it is somewhat dated, unfortunately. (Even with a language designed for fault-tolerance from the ground up, bad things can happen ;-) Sorry for the inconvenience! Dominique

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Tail call elimination with GCC
by Yannick Gingras 11 Avr '08

11 Avr '08

Greetings Lispers of Montréal, I just did some test with GCC's tail call elimination. The result is quite impressive: the tail recursive version of a Mandelbrot set generator runs faster than the iterative one. http://ygingras.net/b/2008/4/tail-call-elimination-is-good-in-c-too I still don't know how to explain this. At the very least, the recursive version should be slower by one extra function call. Anyone knows how it's possible to produce better machine code for the tail recursive version? Best regards, -- Yannick Gingras

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Reminder: Meeting of the MSLUG this week on Thursday
by Guillaume Germain 25 Mar '08

25 Mar '08

Hi everybody, this is a reminder for the next meeting of the MSLUG that will take place this Thursday at 7pm at Université de Montréal. --- What: Montreal Scheme/Lisp User Group Meeting -- Scheme for the Novice and Beyond Where: Room 3195, André-Aisenstadt Building, Université de Montréal, 2920 chemin de la Tour (you can find a plan of the UdeM campus here: http://www.stcum.qc.ca/metro/images/c56.pdf) When: *Thursday* March 27th 7pm Marc Feeley will give a presentation titled "Scheme for the Novice and Beyond". This is intended as a tutorial on Scheme that will also expand on more advanced uses of the language and of the Gambit-C implementation of Scheme. --- As always, the meeting is open to everybody and after the presentation we'll go down to the pub for beer & discussion. See you on Thursday! Guillaume

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University of Waterloo replacing Java by Scheme for intro courses
by Guillaume Germain 20 Mar '08

20 Mar '08

Starting in Fall 2008, all of the first-term courses in the Faculty of Mathematics at Waterloo will use Scheme as a programming language: http://compsci.ca/blog/computer-science-at-waterloo-the-new-scheme-of-thing… Guillaume

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Re: [MSLUG] Google Summer of Code
by Patrick Logan 15 Mar '08

15 Mar '08

(Em, been sending these to the wrong list all day. Here they are...) Other thoughts for the summer of code... * I don't know if such a thing exists already: use SWIG to generate the FFI for C libraries. * Languages running on Gambit: e.g. implement Ruby or Javascript compiling to Gambit, at least simple demonstrations of those languages for the summer. A neat demo would be subsets of Ruby, Javascript, and Scheme compiling into their own shared-nothing processes (much like Termite), and allowing them to pass constant Scheme data or maybe JSON structures back and forth to each other. (And then use that XMPP client I suggested earlier to pass these things to other Gambit processes on other machines.)

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Fwd: Google Summer of Code
by Patrick Logan 15 Mar '08

15 Mar '08

(Em, been sending these to the wrong list all day. Here they are...) Also, in favor of an XMPP-based project... that's what Google talk uses, so it should be in their interest as well.

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Re: [MSLUG] Google Summer of Code
by Patrick Logan 15 Mar '08

15 Mar '08

(Em, been sending these to the wrong list all day. Here they are...) I don't think there is widespread of demand or interest in AMQP, not to mention awareness. Before investing much effort there, I'd look for more popular protocols such as HTTP and/or XMPP, either client or server. Given there are at least two good open source XMPP servers (ejabberd/erlang and openfire/java) the best place to begin may be with a Scheme-based XMPP client.

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Google Summer of Code
by Marc Feeley 14 Mar '08

14 Mar '08

Hello Gambit and Snow users. I will be applying to the Google Summer of Code program as a mentoring organization and propose projects for advancing the development of Gambit, Snow, and Termite. I'd like to start a collective brainstorming exercice to come up with a list of specific projects. If you are interested in participating as a student, please respond to this message (preferably on the mailing list). Please describe briefly what you would like to work on. If you cannot participate (e.g. you are not a student) but have project suggestions, then please speak up on the mailing list. Some projects ideas that come to mind: - native thread support - real-time/parallel GC - closer integration of Termite and Gambit - Gambit packages - web framework - documentation - François Pinard's projects (see MSLUG mailing-list archive) Marc

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Next meeting of the MSLUG: Thursday March 27th 7pm -- "Scheme for the Novice and Beyond"
by Guillaume Germain 11 Mar '08

11 Mar '08

Hi everybody, this is an announce for the next meeting of the MSLUG. What: Montreal Scheme/Lisp User Group Meeting -- Scheme for the Novice and Beyond Where: Room 3195, André-Aisenstadt Building, Université de Montréal, 2920 chemin de la Tour (you can find a plan of the UdeM campus here: http://www.stcum.qc.ca/metro/images/c56.pdf) When: *Thursday* March 27th 7pm Marc Feeley will give a presentation titled "Scheme for the Novice and Beyond". This is intended as a tutorial on Scheme that will also expand on more advanced uses of the language and of the Gambit-C implementation of Scheme. We will try to reach a broader audience this time with this presentation, so please spread the word and invite people that you think might be interested in learning more about Scheme and Lisp. I should be able to post an abstract of the presentation shortly. See you there! Guillaume

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