example.lisp

;; This is a brief example of how introspective and intercessory functionality
;; can be encapsulated in a method combination without changing method
;; definitions or client code. Different implementations of the same method are
;; chosen randomly at runtime and the method combination profiles them to learn
;; which ones are more efficient and starts to call them more often than the
;; others.

(defgeneric sleep-and-stuff ()
  (:method-combination adaptive-optimizer
                       
                       ;; You can easily create an interface to parameterize a
                       ;; method combination like a higher-order function.
                       :sensitivity 11
                       :optimizer-type :moving-average
                       :max-history 1000)
  
  (:method ()
    (sleep (+ 0.003 (* (random-uniform) 0.001))))
  
  (:method
      
      ;; The method combination can looks for special patterns in method
      ;; qualifiers to provide special new functionality beyond the standard
      ;; :before, :after, and :around combination style
      :alt :v1
      
      ()
    (sleep (+ 0.006 (* (random-uniform) 0.001))))
  
  (:method :alt :v2 ()
    (sleep (+ 0.007 (* (random-uniform) 0.001))))
  
  (:method :alt :v3 ()
    (sleep (+ 0.008 (* (random-uniform) 0.001))))
  
  (:method :alt :v4 ()
    (sleep (+ 0.011 (* (random-uniform) 0.001))))
  
  (:method :before ()
    (format *debug-output*
            "Standard :before, :after, and :around methods can still be used...~%"))
  
  (:method :after ()
    (format *debug-output*
            "... for debugging or whatever.~%")))


;; sample client code:
(iter (for i from 1 to 1000)
      (sleep-and-stuff))

;; sample result after 1000 calls (the audience will see these numbers changing live at runtime):

;; call probability | average execution time | number of calls | method variant
.93865|  4.02159| 935.0|NIL
.03407|  7.34107|  36.0|(ALT V1)
.01964|  7.98063|  19.0|(ALT V2)
.00682|  9.26465|   7.0|(ALT V3)
.00082| 12.00000|   2.0|(ALT V4)