Author: Uri Blass
Date: 05:16:49 06/09/04
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On June 09, 2004 at 05:36:44, Peter Berger wrote: >On June 09, 2004 at 03:54:25, Mark Winands wrote: > >>2. The tournament will be an 11-round Swiss-system event, using standard >>(non-accelerated) Swiss pairings. The provisional playing schedule was given on >>page 293 of the December issue. > >In case there were only 13 participants I wonder if it would really be possible >to do legal Swiss pairings for 11 rounds - probably not. > >Someone sent me an interesting thought experiment some time ago. > >Assume a Swiss event with six players, A-F - A is the highest seed. > >1st round: > >A-D 1-0 >E-B 0-1 >C-F 0-1 > >2nd round: > >A is paired first, F gets downfloat and has already played C, thus: > >B-A 1/2 >F-E 1/2 >D-C 1/2 > >Standings: > >A:1.5 (WB) >B:1.5 (BW) >F:1.5 (BW,d) >C:0.5 (WB) >D:0.5 (BW) >E:0.5 (WB,u) > >F already had downfloat, so it's B's turn. A gets F, B gets C, so: > >3rd round: > >A-F >C-B >E-D > >Whatever the results of the 3 round now, there are no legal pairings for round >4. > >It is possible that there is some mistake in the above, but I don't think the >principal problem can be avoided. > >Peter It means that A-F C-B E-D is illegal pairing after A-D E-B C-F B-A F-E D-C I expect every intelligent program that calculates pairing not to do that pairing. What is bad about the following pairing for the 3th round? B-F A-C D-E It allows for the 4th round: E-A C-B F-D Uri
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