Author: José Carlos
Date: 04:23:47 03/08/00
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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 think that there are programs that evaluate only third repetition in the game >and second repetition in the search as a draw(probably Ferret). > >I think that the expected elo gain from this idea against humans is small(I >guess not more than 10 elo rating improvement) > >Uri
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