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A Flaw in Chess Computer Programs

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  • A Flaw in Chess Computer Programs

    I'm not one for computer analysis, but I do on that rare occasion use computers. I've come across a class of position that the computer seems to not see as a draw; that is, those with opposite colored bishops which are certainly drawn. For example:

    In this position, White is a pawn down, so he is not playing to win! Playing to draw, he simply needs to keep his king on the h-file and laugh at Black if he does not admit to a draw. The computer assigns ~1.2 points in Blacks favor. In any forced draw, it should read 0.00.

    In this position, Black is two pawns up. He cannot win, though. All White need do is take control of a square in front of the h-pawn with his bishop (taking the pawn when it advances, sacrificing itself if necessary) and run his king over to the a1-a2-b1-b2 sqaure where Black's light square Bishop and King cannot force White's king from protecting the Queening square (your run-of-the-mill wrong Rook pawn endgame). Somehow, though, ~3 points in Black's favor to the computer. This position actually caused quite an argument on which, even when a titled player (IM) came and refuted anyone saying it was a win for Black, persisted for months!

    This is just one flaw in many computer programs, and one reason I am wary of computer analysis. Any thoughts?
    Last edited by Someone2841; 10-18-2012, 12:59 AM.

  • #2
    In both cases these demonstrate the horizon effect. Everybody knows that computers are weak in endgames where depth of searching is particularly important. This is why computers use tablebases.

    The easiest way to beat a computer is to maneuver it into a position where there are tactics just beyond it's horizon. This is why closed positions work - humans can see tactics behind the pawn structure better than a computer which has to calculate all the way there. Opposite-side-castling often works becasue the resulting pawn storms require lots of ply which can push the results outside the computer's search depth.

    With fast enough computer and enough time and/or memory, a computer would get both of those positions correctly.


    • #3
      Just wait until they have 32 piece tablebases...


      • #4
        You never mentioned which engine.
        Alexander Alekhine is my chess hero.

        An eerie chess short story: The Empty Chair

        My newest chess story: Gamble: A Supernatural Chess Tale


        • #5
          There are many positions that we should not trust a computer's evaluation one of them is rook pawn endgames.. Here is the comment of stockfish programmer in his code..

          Rook pawns are a special case: They are sometimes worse, and sometimes better than other passed pawns. It is difficult to find good rules for determining whether they are good or bad. For now,we try the following: Increase the value for rook pawns if the other side has no pieces apart from a knight, and decrease the value if the other side has a rook or queen.
          " Deep calculation is not what distinguishes the champions. It does not matter how far ahead you see if you don't understand what you are looking at. When I contemplate my move, I first must consider all the elements in the position so that i can develop a strategy and develop intermediate objectives"

          -- Garry Kasparov--

          "Tactics must be guided by strategy"

          --- Garry Kasparov--


          • #6
            Originally posted by Octal View Post
            Just wait until they have 32 piece tablebases...
            LOL atm for a normal desktop computer 6 pieces tablebases is the max. For a 7 pieces tablebase you need 70 TB of disk space according to this forum: 7 Piece Nalimov tablebases. Imagine how long we have to go for 32 pieces tablebase.
            Last edited by Sammy39337; 10-18-2012, 11:07 AM.


            • #7
              It may not take that long if they use those (shredded document restoring)kids from the movie Argo
              I float like a pawn island and sting like an ignored knight