16.1 Performance of Byte-Compiled Code

A byte-compiled function is not as efficient as a primitive function written in C, but runs much faster than the version written in Lisp. Here is an example:

(defun silly-loop (n)
  "Return time before and after N iterations of a loop."
  (let ((t1 (current-time-string)))
    (while (> (setq n (1- n))
              0))
    (list t1 (current-time-string))))
⇒ silly-loop

(silly-loop 100000)
⇒ ("Fri Mar 18 17:25:57 1994"
    "Fri Mar 18 17:26:28 1994")  ; 31 seconds

(byte-compile 'silly-loop)
⇒ [Compiled code not shown]

(silly-loop 100000)
⇒ ("Fri Mar 18 17:26:52 1994"
    "Fri Mar 18 17:26:58 1994")  ; 6 seconds

In this example, the interpreted code required 31 seconds to run, whereas the byte-compiled code required 6 seconds. These results are representative, but actual results will vary greatly.

Ce document a été généré par Eric Reinbold le 13 Octobre 2007 en utilisant texi2html 1.78.