Author: James T. Walker
Date: 05:38:23 03/30/99
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On March 30, 1999 at 05:24:39, Sylvain Renard wrote: >>>I found a position when Junior (using tablebases) goes wrong in the winning side >>>of KRP vs KR >>>6R1/7k/5P2/8/8/8/7r/K7 w - - 0 1 >>>Fritz's tablebases show the right winning move 1.f7 (8) (I do not understand >>>8) but after this move the tablebases show for black Rf2 with draw. > Yes, good work! But this is kind of error is easy to understand >because on Fritz CD ROM there are the Ken Thompson's files : Pr_r.g, >Rb_r.g, Rn_r.g but the file Rr_r.g is missing. After 1...Rf2, the only >winning move is 2.f8R!! all other moves lead to a draw. > >>At that point white has a "Won" endgame and abandons the CD ROM because it >>believes the program can win the game from there. >No it is because it does not have the good file on the CD! The file Rr_r.g >is missing. > >>Yes, this is an error in the tablebase. >Because it is uncomplete. > ********** Hello Sylvain, I don't think the missing tablebase should matter ! If your tablebase would simply tell your program to promote to a Rook from that point on it is a won game and no tablebases are needed. The error in the tablebase is in not promoting to a rook. When it promotes to a bishop it is drawn. That is the error. Most any program can win 2 rooks vs 1 rook or KR vs K. Jim Walker ************** >>>I am not sure about the result of 2.f8Q, the only question is if black has a >>>perpetual check and I did not analyze this position and did not check it with >>>KQR vs KR tablebases. >If you have Ken Thompson CD N°1 (and for instance ChessBase) you >can check it's a draw. > >>Yes, I believe the 2. f8=Q is a draw because of moves like Ra2+. >>Jim Walker >It is confirmed both by Ken Thompson database (when complete...) >and Edward's tablebases (and human thinking too!). > >My program Capture uses Edward's tablebases. It plays 1.f7 and >announces mate in 20 moves. I have also checked that after >1.f7 Rf2 2.f8Q?? it plays 2...Ra2+ and announces a draw. > > Best regards, >Sylvain Renard
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