Below are some timing LISP routines which may be helpful. They are
provided by Mauricio Herandez, a former student.....


 
;;
;; Stop-clock routines.
;; 
;; Written by Mauricio A. Hernandez for W4701, October 1995.
;;            Department of Computer Science, Columbia University.
;; The author can be reached at mauricio@cs.columbia.edu
;;
;; How to use:
;; 
;; > (start-timer 'my-clock)
;; ;; The current time, in internal form, is returned
;; > ;; Do your functions here.
;; > ;;
;; > (stop-timer 'my-clock)
;; ;; The current time, in internal form, is returned
;; > (clock-time 'my-clock)
;; 20.34524
;;
;; Your function took 20.3 seconds to complete.
;; Notice that you can have several clocks "running" in your program.
;; at the same time.  Just give a different name to each one.  Also,
;; STOP-TIMER does not actually stops the clock but rather records the
;; current time for the use of the next CLOCK-TIME call.  In other
words,
;; you can "stop" the clock as many times you want to check the time
;; at different intervals of your program.  For example:
;;
;; > (start-timer 'stop-clock)
;; ;; as before, the real time is returned
;; > ;; Let me wait 20 secs.
;; > (stop-timer 'stop-clock)
;; ;; as before, the real time is returned 
;; > (clock-time 'stop-clock)
;; 20.48349
;; > ;; Now I wait another 20 secs and stop the timer again.
;; > (stop-timer 'stop-clock)
;; ;; another number appears
;; > (clock-time 'stop-clock)
;; 40.34533
;;
;; You can also use STOP-AND-RETURN-TIMER to stop and return the
;; interval time.  This function is equivalent to a call to STOP-TIMER
;; followed by CLOCK-TIME. 
;;
 
(in-package 'user)
 
 
(defun start-timer (timer)
  (progn
     ;; Get the Real System time.
     (setf (get timer 'start-time) (get-internal-real-time))
     ;; Reset the stop-time.
     (setf (get timer 'stop-time) (get timer 'start-time))))
 
(defun stop-timer (timer)
   ;; Set the stop time to the system real time.
   (setf (get timer 'stop-time) (get-internal-real-time)))
 
(defun stop-and-return-timer (timer)
  (progn
     ;; Set the stop time to the system real time.
     (setf (get timer 'stop-time) (get-internal-real-time))
     (clock-time timer)))
 
(defun clock-time (timer)
   ;; Return the difference between the stop-time and start-time.
   (/ (- (get timer 'stop-time) (get timer 'start-time)) 1000000.0))