rect.lisp

(declaim (optimize (speed 3) (safety 0) (debug 0) (compilation-speed 0)))

(defconstant *size* 20000)
(defconstant *rect* 999)
(defconstant *full* (+ 1 *rect* *size*))
(defconstant *rect-count* 2000)

(defun make-prng ()
  (let ((s 123456789))
    (lambda ()
      (prog1 s
        (setf s (mod (+ (* s 22695477) 12345) 1073741824))))))

(defun make-rect-generator ()
  (let ((prng (make-prng)))
    (lambda ()
      (vector (mod (funcall prng) *size*)      (mod (funcall prng) *size*)
          (1+ (mod (funcall prng) *rect*)) (1+ (mod (funcall prng) *rect*))))))

(defun area-fill (area rect)
  (dotimes (y (aref rect 3) rect)
    (dotimes (x (aref rect 2))
      (setf (aref area (+ x (aref rect 0)) (+ y (aref rect 1))) 1))))

(defun area ()
  (let ((area (make-array (list *full* *full*) :element-type 'bit))
        (gen (make-rect-generator))
        (sum 0))
    (dotimes (i *rect-count*)
      (area-fill area (funcall gen)))
    (dotimes (y *full* sum)
      (dotimes (x *full*)
        (when (= (aref area x y) 1)
          (incf sum))))))

(time (format t "Area: ~:d units~%" (area)))