;;;; 2007-03-20 22:35:43
;;;; This is your lisp file. There are many like it, but this one is yours.
;;;; Iterative Improvement Search Algorithms

(defun between (min max)
  (+ min  (* (random 1.0) (- max min))))

(defun mutate (current)
  (mapcar #'(lambda (part)
              (let* ((old (cdr part))
                     (new (+ old (between -0.5 0.5))))
                (cons (car part) new)))
          current))

(defmacro at (key l) `(cdr (assoc ,key ,l)))

(setf *cache*  (make-hash-table))
(setf *things* (make-hash-table))

(defstruct thing name generator)

(defmacro def (name generator)
   `(setf (gethash ',name *things*) 
          (make-thing :name ',name 
                      :generator #'(lambda () ,generator))))
(def a (between 2 3))
 
(defmacro ? (key)
  (let* ((default :sOmCrazyMizSpeltSymBBol)
         (tmp      (gethash ',key *memos* default)))
    (if (eq tmp default)
        (funcall (gethash ',key *things* 'missing))
        tmp)))
      
(register 'a (between 10 20))

(defun start () `((a . 1) (b . 1)))
(defun cost (l)
  (let ((a (at 'a l))
        (b (at 'b l))) 
    (abs (+ (* 3 a ) (* -1 b) 2))))

(defun metropolis (&key (steps 10000)
                        (cost 'cost)
                        (next 'mutate)
                        (first 'start)
                        (near  0.001))
  (let* (best
          (time 1) 
          (bestS (expt 10 32))
          new
          newS
          (current (funcall first))
          (currentS (funcall cost current)))
    (loop
      (if (<= time 0 ) 
          (return (values best bestS)))
      (setf new  (funcall next current)
            newS (funcall cost new))
      (if (< newS bestS)
          (setf best   (copy-list new)
                bestS  newS))
      (if (accept (- newS currentS) time)
          (setf current  (copy-list new)
                currentS newS))
      (setf time 
            (- time (/ 1.0 steps)))
      )))

(defun accept(delta time)
  (or (<= delta 0)
      (< (random 1.0)
         (expt 2.781281828 
               (* -1.0 (/ delta time))))))