The 3rd Prolog Programming Contest

Appeared in Volume 10/1, February 1997

Bart Demoen

The third Annual Prolog Programming Contest took place in Bad Honnef (near Bonn) on September 2nd 1996 during JICSLP'96.

The conference organisers (thank you Univ. of Bonn, Rainer Manthey and Lutz Plumer) provided 10 machines, so nine teams could participate. Every team had three members, including celebrities such as the ALP President and the current, and next, JICSLP Program Chairs.

In principle, people can preregister for this contest, but of course they never do. The exception was the winners of the previous two contests: the Melbourne team. So eager to win again, perhaps? At the reception before the conference, I encouraged more people to take part, and it seems that people find it difficult to say no.

As in previous years, SICStus Prolog was used: thank you SICS for providing a free license for the contest. Also thanks to Thomas Fuchs for his great and punctual help, both before and during the competition. He had a tough time because, one hour before the contest, two machines broke down, and he only got them fixed a few minutes before the contest started.

Since the Melbourne team had won this event twice before, it was hoped that a good challenger would turn up. In any case, it seemed not unthinkable that the Melbourne team could be defeated: after its victory in 1994 with a large margin, it had only won in 1995 by a few seconds over the Upsalla team. Personally, I thought Upsalla might win this time, as it had done consistently so well in previous contests. Unfortunately, the Upsalla team could not participate this year.

The teams were given 5 problems, and 2 hours to solve them. If no team had at least 3 solutions, there would be no winner. And at one point, I really thought that there would be no winner. It was 59 minutes before the Melbourne team handed in the first correct solution. They led at that point, even though Fergus Henderson had corrupted a machine in such a way that it had to be rebooted from CD-ROM. The Melbourne team could not type on their machine for over 15 minutes.

Maybe the problems were too difficult?

But, 2 minutes after the Melbourne team, another team submitted its first correct solution! And then all the teams started submitting at a high rate. Still, there weren't that many good solutions, and under pressure people made very strange mistakes indeed. For example, the number of optimal paths had to be computed in one problem, which is clearly a positive integer, but one team managed to get 2.5! Perhaps a typed language would have helped them :-) Another team wasn't sure where to put a crucial "cut", and I saw them test their program three times, with the cut at different places, until they thought they had it right.

A bit more about the 9 teams: there were five teams made up of people from single countries: a Spanish team (even though they had a German member), French, Italian, Belgian and Australian teams. The other teams were more international: a Bin-XSB team, a completely non-German team mainly from Munich, an Israeli-American team, and one team representing Asia, Australia and America.

Now the result: the Melbourne team was not just defeated, it was completely destroyed! As were all the other teams. Indeed, the winning team solved four problems, while the second team -Leuven - solved two. Melbourne - like four other teams - solved only one problem!

The winning team, consisting of Slim Abdenadher, Francesco Bugliesi and Thomas Fruewirth, brought victory to where it naturally belongs: Europe. Congratulations to them for an impressive exhibition of programming skill! This team forces the organisers of next year's contest to set very high standards indeed.

Talking of next year, there will probably be a 4th contest at ICLP'97 in Leuven, held from July 8th till 12th (workshops included). I hope to see you there. In case you feel like contributing to the next contest, or organising it, please contact me.

The problems from all the contests are available from my home page http://cs.kuleuven.ac.be/~bmd. But don't expect to find the solutions :-)

Thanks again to all the people who made the contest possible and/or participated.

Bart Demoen
Email: bmd@cs.kuleuven.ac.be

P.S. I wonder whether the Australian newspapers covered this contest in the same depth as last year :-)