diff options
| -rw-r--r-- | chess-ai.el | 91 |
1 files changed, 65 insertions, 26 deletions
diff --git a/chess-ai.el b/chess-ai.el index bd05f5e..7aeabe8 100644 --- a/chess-ai.el +++ b/chess-ai.el @@ -27,45 +27,84 @@ (require 'cl) (defgroup chess-ai () - "A simple chess engine written in elisp." + "A simple chess engine written in elisp. + +This module does not allow for configuring search time used to calculate +reply moves. You can only specify the search depth (see `chess-ai-depth')." :group 'chess) (defcustom chess-ai-depth 2 - "*The depth used to prune the search tree." + "*The default depth used to prune the search tree." :group 'chess-ai :type 'integer) -(defvar chess-pawn-value 100) -(defvar chess-knight-value 300) -(defvar chess-bishop-value 300) -(defvar chess-rook-value 500) -(defvar chess-queen-value 900) -(defvar chess-king-value 10000) +(defcustom chess-ai-pawn-value 100 + "*Value of a Pawn." + :group 'chess-ai + :type 'integer) + +(defcustom chess-ai-knight-value 300 + "*Value of a Knight." + :group 'chess-ai + :type 'integer) + +(defcustom chess-ai-bishop-value 300 + "*Value of a Bishop." + :group 'chess-ai + :type 'integer) + +(defcustom chess-ai-rook-value 500 + "*Value of a Rook." + :group 'chess-ai + :type 'intger) + +(defcustom chess-ai-queen-value 900 + "*Value of a Queen." + :group 'chess-ai + :type 'integer) + +(defcustom chess-ai-passed-pawn 50 + "*Extra Score for a passed Pawn." + :group 'chess-ai + :type 'integer) (defun chess-eval-static (position) - "Find the static score for POSITION." + "Calculate the static score for POSITION." (assert (vectorp position)) (let ((v 0) (status (chess-pos-status position))) (if (eq status :checkmate) - -64000 + -32767 (if (eq status :stalemate) - v - (dotimes (i 64 (if (chess-pos-side-to-move position) v (- v))) - (let ((piece (aref position i))) - (cond - ((= piece ?P) (incf v chess-pawn-value)) - ((= piece ?p) (decf v chess-pawn-value)) - ((= piece ?K) (incf v chess-king-value)) - ((= piece ?k) (decf v chess-king-value)) - ((= piece ?Q) (incf v chess-queen-value)) - ((= piece ?q) (decf v chess-queen-value)) - ((= piece ?R) (incf v chess-rook-value)) - ((= piece ?r) (decf v chess-rook-value)) - ((= piece ?B) (incf v chess-bishop-value)) - ((= piece ?b) (decf v chess-bishop-value)) - ((= piece ?N) (incf v chess-knight-value)) - ((= piece ?n) (decf v chess-knight-value))))))))) + 0 + (let (white-pawns black-pawns) + (dotimes (i 64) + (let ((piece (aref position i))) + (unless (= piece ? ) + (cond + ((= piece ?P) (push i white-pawns) (incf v chess-ai-pawn-value)) + ((= piece ?p) (push i black-pawns) (decf v chess-ai-pawn-value)) + ((= piece ?Q) (incf v chess-ai-queen-value)) + ((= piece ?q) (decf v chess-ai-queen-value)) + ((= piece ?R) (incf v chess-ai-rook-value)) + ((= piece ?r) (decf v chess-ai-rook-value)) + ((= piece ?B) (incf v chess-ai-bishop-value)) + ((= piece ?b) (decf v chess-ai-bishop-value)) + ((= piece ?N) (incf v chess-ai-knight-value)) + ((= piece ?n) (decf v chess-ai-knight-value)))))) + ;; Reward passed Pawns + (unless white-pawns + (setq v (+ (* (length + (chess-pos-passed-pawns position t white-pawns)) + chess-ai-passed-pawn)))) + (unless black-pawns + (setq v (- v + (* (length + (chess-pos-passed-pawns position nil black-pawns)) + chess-ai-passed-pawn)))) + (if (chess-pos-side-to-move position) + v + (- v))))))) (defun chess-ai-eval (position depth alpha beta &optional line) "Evaluate POSITION using a simple AlphaBeta search algorithm using at most |