Saturday, 31 August 2013

Finding a clear winner

The organisers of the Best in the West tournament, which is currently being held in Melbourne, have made a brave choice in sticking with a 5 round open tournament. This is despite the event attracting 80+ players, which is well above the number of players a 5 round event could be expected to cope with.
I suspect one, somewhat pleasant, reason for this is they did not expect such a large entry, and stuck with the format they had used for previous years.
The general principle for swiss event is that you need at least log2N rounds to find a clear winner. Of course additional rounds above that number are desirable, to allow the minor places to be determined with some accuracy.
In practice this formula does not always hold, as drawn games will reduce the number of players on perfect scores. And on the flip side, having this number of rounds will not always guarantee an outright first. The most extreme local example of this may well be the 1978 Doeberl Cup, where there was an 8 way tie for first place. The tournament was a 96 player Open, played over 7 rounds. The winning score was 5.5/7 and IM Robert Jamieson won the cup on countback.

1 comment:

Anonymous said...

I think it depends on the players in the tournament - for an U2000 event there aren't likely to be many draws and therefore 5 rounds isn't really enough to split the field, but if there's a lot of depth at the top then there'll almost always be a number of draws on the top boards over the five rounds, and there will be enough rounds to determine the just winner even if the minor placings are determined by and large on the 'luck of the draw'. One solution would be to split such a tournament into two sections (e.g. U1600 and Open).