diff options
| -rw-r--r-- | chess-ai.el | 20 |
1 files changed, 10 insertions, 10 deletions
diff --git a/chess-ai.el b/chess-ai.el index 65099b9..9bc4a9c 100644 --- a/chess-ai.el +++ b/chess-ai.el @@ -1,4 +1,4 @@ -;;; chess-ai.el --- A Chess playing module +;;; chess-ai.el --- A native Emacs Lisp Chess playing module ;; Copyright (C) 2014 Free Software Foundation, Inc. @@ -204,31 +204,31 @@ index." ;;;; Searching -(defun chess-ai-eval-2 (position achievable cutoff eval-fn) +(defun chess-ai-quiescence (position achievable cutoff eval-fn) "Try to find a quiet position by evaluating only capturing moves." (let ((stand-pat (funcall eval-fn position))) (if (>= stand-pat cutoff) cutoff - (when (< achievable stand-pat) + (when (> stand-pat achievable) (setq achievable stand-pat)) (cl-loop for ply in (chess-ai-plies position t) - for value = (- (chess-ai-eval-2 + for value = (- (chess-ai-quiescence (chess-ply-next-pos ply) (- cutoff) (- achievable) eval-fn)) - when (>= value cutoff) return cutoff - when (> value achievable) do (setq achievable value)) + when (> value achievable) do (setq achievable value) + until (>= achievable cutoff)) achievable))) -(defun chess-ai-eval-1 (position depth achievable cutoff eval-fn) +(defun chess-ai-search (position depth achievable cutoff eval-fn) (if (zerop depth) (if chess-ai-quiescence - (chess-ai-eval-2 position achievable cutoff eval-fn) + (chess-ai-quiescence position achievable cutoff eval-fn) (funcall eval-fn position)) (let ((plies (chess-ai-plies position))) (if (null plies) (funcall eval-fn position) (cl-loop for ply in plies - for value = (- (chess-ai-eval-1 (chess-ply-next-pos ply) + for value = (- (chess-ai-search (chess-ply-next-pos ply) (1- depth) (- cutoff) (- achievable) eval-fn)) @@ -257,7 +257,7 @@ and `car' is the score of that move. If there is no legal move from POSITION, 0 (length plies)))) (cl-loop for i from 1 for ply in plies - do (let ((value (- (chess-ai-eval-1 + do (let ((value (- (chess-ai-search (chess-ply-next-pos ply) (1- depth) (- cutoff) (- achievable) eval-fn)))) |