Author: Ingo Lindam
Date: 16:13:00 12/10/02
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On December 10, 2002 at 18:53:21, Mike S. wrote: >Maybe it should be called "The Mig Fortress" better, because it'S Mig's >comprehensive analysis of game no. 6 of the Bahrain match which ends with this >position: > >[D]8/5k1p/5q2/8/1R6/6P1/5P2/6K1 b - - 0 45 > >White's rook can go to f4 or h4, and "Black has no way through the fortress." > >http://www.chessbase.com/images2/2002/bahrain/games/mig6.htm (see after the last >move on the bottom of the page) > >I think the fortress idea is something especially difficult for chess programs, >because it's very "general", IOW not related to a special pattern or material >balance. > >I wonder if an idea from the incomplete tbs. problem could be used to detect >fortresses: With the pawn just before the promotion, but the tablebases for the >resulting material missing, the idea was like: "If it's # in 14, but one move >later *not* # in 13 or less, then there must be something wrong and I have to >promote the pawn (even if the eval is less than mate then, at first)." > >The situation is somewhat similar in a fortress position, when one side has a >more or less huge material advantage (which would normally be capable of >winning), but can't make any significant progress for a long series of moves. > >Testing such a detection would probably require to have the engine actually play >some f moves, so the engine could recognise that there is no progress... >Although, with usual search depths of ~12 or more plies (+ extensions), maybe >that is sufficient for the idea too. > >Are there engines known to have a fortress detection? > >Regards, >M.Scheidl Hi Mike, I don't know an engine having a fortress detection (but that doenn't mean that there isn't any). But couldn't it be a possible way to implement a fortress detection to force the engine to have atleast a single winning plan (not able to detect being impossible) to make a wining score valid? In this special position the would be only three candidates for a winning plan. 1) winning the white rook 2) letting the h pawn pass to h1 3) mate the white king it should be easy to judge for the engine that 1) and 2) are well defended by playing Rf4-h4-f4.... for showing that 3 is impossible also one could introduce jump-moves (means a piece can jump everywhere in a single move when it can reach this square in N moves) or even show just by floodfilling without jump-moves (?) that here the black king can reach the squares necessary to reach for making a mate possible. Ofcourse this is just brainstorming. Internette Gruesse, Ingo
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