Author: Bruce Moreland
Date: 09:34:36 12/25/02
Go up one level in this thread
On December 25, 2002 at 06:21:23, Gerd Isenberg wrote: >On December 24, 2002 at 19:38:27, Vincent Diepeveen wrote: > >>On December 24, 2002 at 03:40:24, Bruce Moreland wrote: >> >>>A backward pawn has the following attributes: >>> >>>1) It cannot be defended by a pawn. >>>2) If it advances, it will be captured by an enemy pawn. >>>3) It is now, or can advance to become, the base of a pawn chain. >>> >>>The classic case is black pawns d6, e5, white pawn e4. >>> >>>The pawn doesn't have to be on an open file. >>> >>>I argue that the pawn cannot be a member of a duo, >> >>I disagree. Some pawns can be member of a duo and backward. >> >>For example white Rb1,c5 >>black b7,c7 Kc8 >> >>b7 is backward. c5 is not. It is isolated. > > >Hi Vincent, > >That's interesting. >I thought backwardness is independent of pieces (per definition) and could >therefore been calculated without considering pieces and stored in the >PawnHash-Table?! > >What is the exact reason whether c5 is not backward. >1. no candidate >2. if two opponent pawns have backward-distance, > the most advanced is not backward. >3. because it's isolated. c5 isn't backward because it is isolated. That's another thing. Black pawns b7, c6, white pawns b6, c5 -- neither of the base pawns are backward, because a piece can't go on the stop square. But take away b6 and b7 is, and take away c6 and c5 is. In vincent's example of c5 vs b7 and c7, if you were to put a white pawn on b5, it can't be argued that anything is wrong with black's pawn structure. Really, this isn't a weak pawn case so much as a dynamic attacking case, and that is the code that should catch this. I think though that if you have c5 versus c6, b7, if you put a white pawn on b4, both b-file pawns are backward: 1) Can't advance to form duo. 2) Friendly pawn "ahead" on adjacent file. 3) Stop square weak. The net effect is artificial isolation, which is why point 2 is there. If there is no friendly pawn on an adjacent file, the pawn is isolated, which is another weak case that can be detected. I don't penalize the duo case because there are often dynamic possibilities when you have a duo. I don't think it is fair to discuss the rook in Vincent's example. If the rook is absent, b7 & c7 versus c5, b7 is not backward, it's a candidate. Static pawn code shouldn't catch this unless it's just to mark it so king safety can understand it. bruce
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