(defun bpt-repeat* (n thunk)
  (while (/= n 0)
    (funcall thunk)
    (setq n (1- n))))

(defmacro bpt-repeat (n expr)
  `(bpt-repeat* ,n (lambda () ,expr)))

(defun bpt-msecs (v)
  (let ((low (cadr v))
        (microsec (caddr v)))
    (+ (* low 1000)
       (/ microsec 1000))))

(defun bpt-%time (thunk)
  (let ((t1 (get-internal-run-time)))
    (funcall thunk)
    (let ((t2 (get-internal-run-time)))
      (assert (= (car t1) (car t2)))
      (- (bpt-msecs t2)
         (bpt-msecs t1)))))

(defun bpt-time* (n thunk)
  (insert
   (format "%d\n"
           (- (bpt-%time `(lambda () (bpt-repeat* n ,thunk)))
              (bpt-%time '(lambda () (bpt-repeat* n (lambda ()))))))))