Author: Robert Hyatt
Date: 20:47:32 03/08/00
Go up one level in this thread
On March 08, 2000 at 09:41:05, blass uri wrote: >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 This is probably wrong. ie I play Ng1-f3 on the board. The next move I might try is Nf3-g1. That is a repetition. That you won't treat as a repetition. This happens more than a few times in the search... Searching below Nf3-g1 until I play Ng1-f3 again takes some work that could be avoided here, leaving open the hole already mentioned...
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