www.delorie.com/gnu/docs/elisp-manual-21/elisp_205.html   search  
 
Buy the book!


GNU Emacs Lisp Reference Manual

[ < ] [ > ]   [ << ] [ Up ] [ >> ]         [Top] [Contents] [Index] [ ? ]

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.


  webmaster   donations   bookstore     delorie software   privacy  
  Copyright 2003   by The Free Software Foundation     Updated Jun 2003