Saturday, 22 November 2008

The Olympiad Pairings Sytem

In a previous post I reported on some comments made concerning the pairing system in use at this years Olympiad. I must confess it wasn't until today that I finally got my head around the whole process.
The system in use is the Burstein System which uses SB tie-breaks to order teams in a score bracket (rather than rating or seeding which is more common). The other complication is that teams in a score bracket are not paired top v middle, but instead top v bottom, second to v second bottom etc
The most difficult challenge facing the teams is to try and work out their SB score, which is a mystery to most. The actual formula used is the sum of your opponents match points multiplied by your game points against them. For example PNG lost 2.5 - 1.5 to the AHO's who until today had 6 match points. This means that they contribute 9 points to our tiebreak. To remove distortion based on unlucky (random?) pairings, you drop the lowest score.
Knowing this clears up some of the confusion about the pairing system, as their was an opinion that winning by a narrow margin (2.5-1.5) actually improved your tie-break (on the principle your opponents were stronger than a team you might beat 4-0). It turns out that this is not the case.


transformation said...

excellent blog. and at 350 to 40o posts, you should be highly experienced by now.

one humble suggestion. much great content, BUT do yourself a favor and set up your blog under settings so that the last 25 or, for you who has shorter posts, maybe the last 50 posts showing.

thus you do not HIDE your riches. if you go to my blog, you will see a decent example of paging down, and seeing post, after post, after post, so peripatetic viewers can quickly scan and find what they want, at random if so! :)

take care, again, thanks, dk

Alex said...

I agree Shaun. Chessexpress is Australia's best chess blog!

Alex Toolsie

Anonymous said...

Thanks for your reports from close-up in Dresden.

I've had the pairing system worked out for a few rounds now, and have predicted (more or less) Canada's pairings. There is also a version of it up on (surprise) FIDE's website, under Olympiad rules, just where you'd expect it.

Here we go:

What continues to mystify me is why odd men (aka floaters) play the bottom team in the next lower group. For example, Ukraine - New Zealand, Netherlands - Faroe Islands, and in round 10, Canada - Nicaragua. I don't see that in the rules, and certainly don't see the logic in it.

Jonathan Berry
IA, GMC, FM. Canada.

Shaun Press said...

Jonathan, this is probably the issue that remains the biggest mystery here as well. At this point there doesn't seem to be an answer!