Author: Peter Fendrich
Date: 06:26:09 06/02/03
Go up one level in this thread
On June 02, 2003 at 07:55:21, Gerd Isenberg wrote: >On June 02, 2003 at 05:11:34, Peter Fendrich wrote: > >>From a game at ICC between TerraPi (Terra) and HenrikM this position arised: >>[D]1k1r3r/pp4b1/3q2p1/3p3p/3P1p2/1Q2pP1P/PP2P1BP/K1RR4 w - h6 >> >>The last move was 22...h5 with the threat h4 and completely lock in the white >>bishop. A very nice maneuver by HenrikM. >>Terra is absolutely unaware of this threat and after 23.Rc3 h4 the white 'lost' >>a piece and later on the game. >>My question is: does any engine know how to handle this position and how? >> >>/Peter > >Hi Peter, > >Some "bad" bishop code should help to avoid these positions. >If the bishop is "behind" pawn rams or other "unmovable" pawns with own pawns on >the same color of the bishop... > >On implemetation idea (for all kind of pieces) is a kind progressive mobilty >determination with Kogge-Stone-Fill algorithm. > >1. determine all none movable pawns, mechanical like rams, but also dynamical >like backward pawns. > >2. generate a special attack set of the bishop, considering only own none >movable pawns and opposite pawns and pieces as occupied bitboard. > >3. if the set contains opposite pieces, the bishop is not considered as "bad". > >4. Otherwise exclude all own none movable pawns and squares dominated by the >opponent from this set. > >5. If the remaining set is empty, the bishop is trapped, perform a appropriate >penalty. > >6. Otherwise if the cardinality of the set is low (eg. < 4), perform one >Kogge-Stone fill from this remaining attack set. If the set don't grows anymore, >the bishop is considred as a "very bad" one. > >MvH, >Gerd Hi Gerd, I was up to something similar even if not directly Kogge-Stone. This problem happens in 1 game out of 200 without being too comitted to precisely this figure. I fear that it is quite costly to do this alg all the time. One should need some kind of trigger to start it I think. Both rooks and bishops and sometimes knights are very vulnerable to this. Even Rooks can be hindered but seldom by pawns only. For example a rook can be, if not trapped, hindered by it's own king (king moves to f1 and g1 while the rook is still on h1). In theory even Queens are subject to this as well but in practice they can chose either the "bishop-way" or the "rook-way" out. Queens are more vulnerable to be trapped behind the opponents pieces but that's another story! Isn't "MvH" Swedish only?? /Peter
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.