Author: Robert Hyatt
Date: 12:04:32 03/08/00
Go up one level in this thread
On March 08, 2000 at 12:12:07, Bruce Moreland wrote: >On March 08, 2000 at 08:34:45, Robert Hyatt wrote: > >>On March 08, 2000 at 05:11:11, Howard Exner wrote: >> >>>Test your chess engine if it handles this repition theme correctly. To do this >>>set up the position below and play the white side yourself. Do not enter the >>>winning move Kh5 but instead play the blunder Kg5. Now let your program play the >>>black side at say game/15. It will of course play Kd5+ which forces perpetual >>>check. After it does that try to trick the program and reply Kg4. >>>Now the test - does your program play the correct Qd1+ or does it blunder and >>>mistakenly repeat the position with Qe4+, assuming that the opponent will >>>blunder again with Kg5? Rebel Century failed this test and assumed white would >>>play again the poor move Kg5. >>>Why would a program do this? Do other programs fall into this trap of assuming >>>a repetition of moves even when not forced? >>> >>>[D]8/4k3/7Q/8/4q1KP/6P1/8/8 w - - >> >>This is a known problem. Most count 2-fold repetition as draw, as if the >>2-fold repetition can be forced with best play, the 3-fold repetition can also >>be forced. In this case it is wrong, but generally it works fine. >> >>fixing this is easy, but the fix is far worse than the problem. Because to >>require the search to see a 3-fold repetition to recognize a draw would make >>most draws too deep to see. > >I've been explaining for years how to fix this. Any 2x rep in the search is >counted as a draw, and any 2x rep in the game history, plus one rep in the >search, is also a draw. The only case that is now considered a draw, which >would not be considered a draw under this system, is one rep in search plus one >rep in game history. That's no longer a draw. that is one way to 'fix' it. but the fix is not exactly free. this makes it harder to see some draws, hard enough that it is possible to not see them until committed. I don't mind letting someone do this trick, as I haven't seen a case where it has cost me anything at all, yet. And the added speed of just saying '2x is a draw' lets me find draws quicker... > >The benefit is that you never have to worry about this very stupid problem >again. > >The drawbacks are: > >1) You may not allow someone who is beating you to take a repetition. > >2) You may play into repetitions yourself, which annoys your opponent and in >some cases may cause you to draw games via the 50-move rule. This is actually >fairly serious, and I still use the old method for very low material endgames >such as KBN vs K, if I'm not using tables. > >bruce
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.