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diff --git a/gnu/games/chess/DOCUMENTATION/HEURISTICS b/gnu/games/chess/DOCUMENTATION/HEURISTICS deleted file mode 100644 index 254b344..0000000 --- a/gnu/games/chess/DOCUMENTATION/HEURISTICS +++ /dev/null @@ -1,122 +0,0 @@ -This file contains a description of GNU's heuristics. - Copyright (C) 1986, 1987 Free Software Foundation, Inc. - -This file is part of CHESS. - -CHESS is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY. No author or distributor -accepts responsibility to anyone for the consequences of using it -or for whether it serves any particular purpose or works at all, -unless he says so in writing. Refer to the CHESS General Public -License for full details. - -Everyone is granted permission to copy, modify and redistribute -CHESS, but only under the conditions described in the -CHESS General Public License. A copy of this license is -supposed to have been given to you along with CHESS so you -can know your rights and responsibilities. It should be in a -file named COPYING. Among other things, the copyright notice -and this notice must be preserved on all copies. */ - - -- requested by main author -Heuristic descriptions for CHESS. - -Revision: 12-16-87 - -Copyright (c) 1987 by John Stanback - - Here is a brief description of the heuristics used in the positional - evaluator of the GNU Chess program. Many heuristics are functions of the - stage of the game which is based on the total non-pawn material remaining - for both sides. - - -PAWNS - The material value of a pawn is 100 points. Isolated pawns get a - penalty depending on which file they occupy: - (12,14,16,20,20,16,14,12) for files (a..h). - Doubled pawns (which are not also isolated) get a penalty of 12 - points. Backward pawns (defined simply as not being defended by a - pawn with the square in front also not defended by a a pawn) are - penalized 6 points. A 4 point penalty is also invoked for each attack - by the opponent to a backward pawn and for a backward pawn on a - half-open file. Pawn Advancement in the centre is given a bonus of - about 4 points per rank in the opening increasing to about 8 points - per rank in the ending. Advancement on the edges is given a lower - bonus. Pawns on the e and d files and on the 2nd rank are given a 10 - point penalty. An additional penalty of 15 points is invoked if these - pawns are also blocked. Pawns within 2 squares of the king are given - a 10 point bonus. Passed pawns are given a bonus for increasing rank - which is a function of stage of the game and of whether the opponent - blocks or attacks one or more squares in front of the pawn or if the - opponents king is in the square of the pawn. This bonus ranges from - about 15 points for a pawn on the second rank up to about 300 points - for a passed pawn on the 7th rank which can't be stopped from - queening. - - -KNIGHTS - The material value of a knight is 330 points. The main heuristic for - knights is a bonus for proximity to the centre. This varies from 0 - points in the corners to 30 points in the centre. Knights are also - given a bonus for being within 2 squares of each enemy piece. This - bonus is a function of the stage of the game, equalling 4 points in - the end game. A penalty of 1 point per square is given for distance - from either king. A bonus of up to 8 points (depends on stage) is - given for knights which can't be driven away by enemy pawns. - - -BISHOPS - The material value of a bishop is 330 points. Bishops are given a - bonus as material falls off the board equalling 10 points in the end - game. Bishops get a bonus for mobility and Xray mobility thru pieces - but not pawns. This bonus ranges from -4 points for a totally blocked - bishop up to 18 points for a bishop attacking 12 or more squares. - Xray attacks on an enemy R,Q,K or any undefended piece are given an 8 - point bonus. Bishops are given a bonus of 14 points if they lie on - the edge of the board up to 22 points if the lie in the centre. A - bishop is given a bonus of up to 5 points for each attack to a square - adjacent to the enemy king. - - -ROOKS - The material value of a rook is 520 points. Rook mobility is handled - similiarly to bishops with a bonus of 0 points if blocked up to 20 - points if attacking 12 squares or more. A bonus of 8 points for Xray - attacks is handled as it is for bishops. Rooks are given a bonus of - 10 points for occupying a file with no friendly pawns and a bonus of - 4 points if no enemy pawns lie on that file. After the opening Rooks - are penalized slightly depending on "taxicab" distance to the enemy - king. - - -QUEENS - The material value of a queen is 980 points. The only heuristic for a - queen is that after the opening it is penalized slightly for - "taxicab" distance to the enemy king. - - -KINGS - Kings are given a penalty for proximity to the centre in the opening - and a bonus for proximity to the centre in the endgame. The penalty - is about 24 points for being in the centre in the opening with a - bonus of about 36 points for being in the centre in the endgame. - Kings are penalized for lying on an open or half-open file or if the - adjacent file closest to the corner is open or half-open. This - penalty is up to 23 points in the opening and goes to zero in the end - game. The King is penalized up to 8 points if there are no pawns - immediately adjacent. A penalty is invoked depending on the number of - "safe" checks available by the opponent. This penalty ranges from 6 - points for one such check to 50 points for 4 or more. Depending on - game stage, Kings are given up to 10 points for castling and a - penalty of up to 40 points for moving before castling. - - -SPECIAL - If more than one piece is "hung" (attacked and not defended or - attacked by an enemy piece of lower value) an extra penalty of 10 - points is invoked for that side and the search may be extended one - ply. Pinned or trapped pieces are treated similarly. A special mating - routine is used if one side has only a king and the other has mating - material. - |
