Alex McFarlane >It is generally accepted that each additional place requires two rounds.<
That assertion was made by W Ritson Morry. I have never seen any attempt to justify it statistically.
To give you one example of why we might want to have more than one place established which is statistically valid. There is the British U21 Championship subsumed within the event. Last year this was won by a rather low score.
Alex Holowczak >unless you had number of players > 2^number of rounds. In which case, you could have two players on 100% who never played each other.<
Because of draws, it is usually possible by almost any system to have perhaps 80 players in a Swiss and end up with no more than one player with 6/6 or even 5/5.
>So with the logic that Swiss pairings are the normal way of doing things, and the Accelerated Pairings are there to solve a problem, you shouldn't use Accelerated Pairings unless the problem exists. Since we have far less than 2^11 players in the British, we don't have the problem. So why should we use Accelerated Pairings?<
You are confusing Seeded Swiss Pairings with Swiss Pairings. There many systems, such as Dubov, Burstein, Lottery. Read my book. Until 1965 lottery was used uniformly in Britain. That has the disadvantage that it is less efficient at finding the 'best' winner but demonstrates no bias against players due to their pre-established ratings. There will be bias, but this will only be observable at the conclusion of the event. Each event will demonstrate different bias. The other problem of a lottery draw is that it is impossible to predict one's opponent. It is also impossible to prove that the arbiter has not fiddled the pairings. The seeded System, of which you are so fond, demonstrates bias against people at the top of the second half. See Keith Arkell's rsults in the 1984 British Championship where after 4 rounds he had played 3 of the 4 GMs. In a later event there were two players who drew their first four games with the same colour. A was towards the bottom of the first half and B towards the top of the second half. A played no rated opponents. B played 4 rated about 2400. It is entirely possible that A felt more aggrieved. It is entirely natural that arbiters will seek systems which show no bias.
One of the reasons for using the Accelerated Pairing System was to reduce the number of mismatches. I will define that as rated 320 points or more different because that is what the London Chess Association chose (320 = 40 grading points roughly). It does result in a very small number of tremendous mismatches in later rounds. The low rated player usually has had to beat two opponents much higher rated than himself.
Alex H >How many rounds should the British have before accelerated pairings aren't used?<
Profesor Elo said to me he thought Accelerated Pairings brought the leading players together too quickly. Lat year Michael Adams had to float through several score groups to find his opponent in the last round. That cannot be ideal. Wth 11 rounds I suspect that would become a very real problem if there were just 40 players. Arguably the lottery Swiss, which was used for the British until the mids-80s, was better when the number of players was 36 at the maximum because it was LESS efficient.
Both Dubov and Burstein seek to balance strength of opponents. We have tried the former. The Reuben System (see page 37 of the second edition of my book) would definitely avoid the bottom of the second half bias. It has only been used once and worked quite well. It takes on some of the aspects of a knockout. Say 80 players. 1v41. 41 wins, he becomes number 1, 1 becomes 41. If they draw 1 becomes 20 and 41 becomes 21. Added rules are needed where two or more players have the same seeding number.
I played one event where 1v80, 79v2 etc. was used throughout (as in the Knockout World Cup). It tremendously favoured the higher rated players, of whom I was one.
Going back to the thread. I am going to Sheffield. But I don't know how to get there with heavy luggage.
The event will be played at a fine venue, very centrally. Sheffield is a much more attractive city than when I first inspected it in the 1980s. At about this time Roger Edwards is being inundated with entries. We will have to wait patiently while he processes them.
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