Author: Miguel A. Ballicora
Date: 13:57:06 08/03/01
Go up one level in this thread
On August 03, 2001 at 15:44:09, Dieter Buerssner wrote: >A small question about chess rules. Assume the following position (which does >not make any other sense, than to show my point): > >[D] 3kr3/8/8/8/3p4/8/4P3/3RK3 w - - 0 1 > >1. e4 > >Now black cannot capture ep. Then just some stupid moves: > >1...Kd7 2. Ke2 Kd8 3. Ke1 > >Again the same postion as after 1. e4. > >3...Kd7 4. Ke2 Kd8 > >Can at this point White claim a draw, by saying "I intend to move Ke1 - 3fold >repetion"? > >I assume yes. If this is correct: Are you handling this correctly in your >chess-engine? Yes, it can be claimed draw because the 3 positions are identical. In neither of those dxe3 is possible. I do not remember the exact wording but the spirit of the rules were that the 3 positions should be "photographically" and "dynamically" identical. I am not handling this in my engine correctly. Even worse, I follow the silly FEN convention about the ep squares so it will think that a draw cannot be claim even if the the black king and black pawn are moved to the left one column. I think I will drop that convention because it is silly and has no advantage. >The reason why I ask. For the position after 1. e4 the engine may set the >ep-square. I am doing this for Yace. It would be rather expensive, to check, if I do to... >the actual ep capture is legal (at least, it would be expensive doing this in >the search). At a later point, Yace will of course recognize, that the >ep-capture is not legal, but then it is too late ... Maybe it is not very expensive to put the correct hash signature after you "play" the move and write it down on the score sheet (you know what I mean, I do not know what kind of structures you use and how you call it). At least it will solve the problems when the first position has been played already and it is not in the tree search. Regards, Miguel >And a related question about Nalimov EGTBs. I have learned, that setting the ep >square for the TB-probing in positions, where no ep capture is possible, returns >invalid results. I recognized this in KNPKN. I earlier just set the ep-square >after any double pawn push. This had now influence on the search/move-generation >logic of my program. But probing of the TB with the ep-square set yielded wrong >results. I fixed this. > >Now, I wonder, if the TBs will work correctly in the above scenario, when it >really looks like the ep capture is possible at first sight, but it is not >allowed, because the pawn is pinned. > >I think, the only available TBs, for this to occure are KXPKP for X=B,R,Q. I >have neither of those, so I can't check. > >Regards, >Dieter
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.