From: lewisd@...00f.net (Derek Lewis)
Date: 2005-02-16T10:16:51+09:00
Subject: Curious regexp behavior

On a whim, I just decided to try an experiment with regexps, to see how
they perform in two slightly different cases.  I wanted to see how using
a single regexp object for many many evaluations performed compared to
using the regexp within the loop.

The scripts I wrote searched through a words file that is 234937 lines
long.

Here's the scripts I wrote, to clarify:
First one:

total = 0
File.open( 'words', 'r' ) { |file|
   file.each_line { |line|
		word = line.chomp 
		total +=1 if word =~ /[a-df-h][aeiou]{2}/
	}  
}     
puts total

Second one:

rexp = /[a-df-h][aeiou]{2}/
total = 0
File.open( 'words', 'r' ) { |file|
   file.each_line { |line|
		word = line.chomp
		total +=1 if word =~ rexp
	}
}
puts total


I expected the second one to be slightly faster, but was surprised to
see that it was actually slightly slower.  I ran each one about 10-15
times, and eyeballed an average.  The results from each run after the
first were pretty consistant.

It's just a curiosity, but does anyone know what might cause them to be
'backwards' like that? :)

-- 
Derek Lewis

===================================================================
      Java Web-Application Developer
 
      Email    : email@lewisd.com
      Cellular : 778.898.5825
      Website  : http://www.lewisd.com

 "If you've got a 5000-line JSP page that has "all in one" support
 for three input forms and four follow-up screens, all controlled
 by "if" statements in scriptlets, well ... please don't show it
 to me :-).  Its almost dinner time, and I don't want to lose my
 appetite :-)."
      - Craig R. McClanahan