Wednesday, April 13, 2011

Additional Swiss Pairing Rules

If you have looked at the latest set of Dutch Pairing Rules in the FIDE handbook, you might notice a couple of additions. In the "Introductory remarks and Definitions" Section (Section A) a couple of clauses have been added to A7. They are

d. While pairing an odd-number round players having a strong colour preference (players who have had an odd number of games before by any reason) shall be treated like players having an absolute colour preference as long as this does not result in additional downfloaters (GA 2001)
e. While pairing an even-numbered round players having a mild colour preference (players who have had an even number of games before by any reason) shall be treated and counted as if they would have a mild colour preference of that kind (white resp. Black) which reduces the value of x (see A.8) as long as this does not result in additional downfloaters, (GA 2001)

It turns out that these clauses have been part of the rules since 2001, but were only included in the handbook this year (I have no idea why btw). But now that they are there what do they mean?
I asked this question of the Chairman of the FIDE Swiss Pairing Program Committee, Christian Krause. He said that what these rules do is deal with the case where a player hasn't played the same number of rounds as other players in the same score bracket (through byes or forfeits). For example, in pairing an even numbered round a player may have played an even number of games (eg only played 4 of the previous 5 rounds), the players mild colour preference (ie opposite the last colour played if they have had 2 whites and 2 blacks), shall be used to calculate x (the number of pairings in a group that do not satisfy all colour preferences), rather than treating the colour preference as 0 or undefined.


Garvin said...

These two new additions have been getting quite a work out on chesschat.

Shaun Press said...

So I've seen. Of course the discussion would be better served if someone simply asked the chairman of the Swiss Pairings Program Committee what they meant (as I did)

JP Hendriks said...

The calculation of "x" has left me with some confusion anyway. In "normal" situations most players have played an even number of games pairing an odd round, and most of them will have a 0 color balance and only a mild color pref (with WB or BW in the last two rounds). Should these players be counted as white preferers or black preferers for the calculation of x, or as "neutral", only their color pref being used for color allocation?