Path: utzoo!attcan!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!uw-beaver!cornell!wilk
From: wilk@fife.cs.cornell.edu (Michael Wilk)
Newsgroups: comp.lang.lisp
Subject: Mirror speeds
Message-ID: <47064@cornell.UUCP>
Date: 13 Oct 90 18:26:05 GMT
Sender: nobody@cornell.UUCP
Reply-To: wilk@cs.cornell.edu (Michael Wilk)
Distribution: comp
Organization: Cornell Univ. CS Dept, Ithaca NY
Lines: 65

Here are some timing results on suggested solutions for the "mirror" function:
I won't reveal the huge list I tried this on, but trust me:  It was big.


-------------------------------------------------------------------------------

My effort:

(defun mirror (x)
  (if (atom x)
      x
      (let ((result nil))
	(dolist (item x)
	  (push (mirror item) result))
	result)))

Elapsed Real Time = 10.66 seconds
Total Run Time    = 10.57 seconds
User Run Time     = 10.55 seconds
System Run Time   = 0.02 seconds
Process Page Faults    =        131
Dynamic Bytes Consed   =          0
Ephemeral Bytes Consed =  1,693,584


-------------------------------------------------------------------------------

By Eliot Handelman and Raja Sooriamurthi, modified slightly:

(defun mirror (x)
  (if (atom x)
      x
      (append (mirror (rest x)) (list (mirror (first x))))))

Elapsed Real Time = 6.52 seconds
Total Run Time    = 6.43 seconds
User Run Time     = 6.43 seconds
System Run Time   = 0.00 seconds
Process Page Faults    =          1
Dynamic Bytes Consed   =          0
Ephemeral Bytes Consed =  2,030,088


-------------------------------------------------------------------------------

By Noritake Yonezawa:

(defun mirror (x) 
  (if (atom x)
      x
      (reverse (mapcar #'mirror x))))

Elapsed Real Time = 2.62 seconds
Total Run Time    = 2.52 seconds
User Run Time     = 2.52 seconds
System Run Time   = 0.00 seconds
Process Page Faults    =          5
Dynamic Bytes Consed   =          0
Ephemeral Bytes Consed =    986,984


-------------------------------------------------------------------------------


-Michael Wilk (wilk@cs.cornell.edu)