Author: Rafael Andrist
Date: 03:00:35 08/04/01
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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"? correct >I assume yes. If this is correct: Are you handling this correctly in your >chess-engine? no, I forgot this, but I recognize 2x rep. inside the search tree, so it isn't a big problem >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 >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 ... I generate only legal moves. So a solution would be to modify the hash key according to the number of legal moves or to check if the e.p.-capture is in the move list. To check if the e.p.-capture is legal during search wouldn't be that expensive too with bitboards. (around 50 cpu cycles I guess) Rafael B. Andrist
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