Author: James T. Walker
Date: 18:42:11 06/16/99
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On June 16, 1999 at 17:25:00, Robert Hyatt wrote: >On June 16, 1999 at 16:32:55, Robert Pope wrote: > >>It has been mentioned that the Swiss Pairing System is designed to find an >>absolute winner in a tournament, but if not enough rounds are played, the >>ordering of the lower places is not obvious. >> >>Is it also true then that the pairing system also does the opposite at the same >>time: finds the absolute worst-performing participant? I don't mean this >>question as an insult to any of the participants. I was just wondering if this >>is what the pairing system would do. >> >>Also, from my understanding, the pairings try to pair opponents with the same >>number of points. What if most or all of the participants with the same point >>score have already played each other? Can they be paired a second time? > > >To answer your first question, it works like this. If you have N opponents, >where N is a perfect power of 2, and you have log2(N) rounds, then you will >know the best player, and the worst player (assuming no draws). But the others >will be distributed from better to worse, but not precisely ordered. If you >do log2(N)+1 rounds, you get the top 2 or 3 and the bottom 2 or 3, but the >middle is still muddled. > >To get perfect ordering, you need N-1 rounds so that everybody plays everybody, >and to improve that you need 2*(N-1) rounds where everyone plays everybody with >both colors. > > >Where this gets messy is if you have too many rounds. The rules for pairing >avoid the same players meeting twice in one Swiss, so there are exception rules >to handle this... Had accelerated pairings been used at the WCCC, this would >have been a bigger problem. With 7 rounds it will be a problem before round 7 >when the two top scores have already played and can't play again, so they get >to play lower-ranked opponents with no easy way to 'break the tie' they have >if they both win... Hello Bob, The rules say if exactly two contestants end up tied its a single play off game. That's easy enough. It gets a little messy if 3 or more end up tied though. Jim Walker
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