Author: blass uri
Date: 06:41:05 03/08/00
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On March 08, 2000 at 07:23:47, José Carlos wrote: >On March 08, 2000 at 06:29:13, blass uri 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? >> >>I believe that many programs falls into this trap because they evaluate second >>repetition as a draw. >> >>It is usually not important against computers because computers do not do >>tactical blunders but it may be important against humans. >> >>The reason that programs do it is that most of the programs were not designed in >>the right way. > > I disagree. I think that is the right way of doing things. Programs (including >mine) test for second repetition assuming both sides played the best moves they >found. Testing third repetition instead of second takes way longer, and you need >two extra plies to find it. > You can choose testing third instead of second, it is not any difficult to >implement, but there will be very few cases where this will help, and a lot of >cases where this will slow down the search: more time for the test, more plies >to find it and you cannot return the draw value in second, so you have to >generate many more nodes. > > Just my opinion, anyway. > > José C. I do not suggest to test for third repetition but only to ignore previous positions in the test for second repetition (with the exception of cases when there was a repetition of previous positions). I do not think that it is going to slow down the search significantly because I believe that most of the repetition in the search are repetitions of positions that were not in the game. Uri
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