From: "Michael C. Libby" <mcl-ruby-talk@...>
Date: 2005-01-10T21:54:34+09:00
Subject: Re: brute force string search

On Mon, 2005-01-10 at 09:51 +0900, Martin Pirker wrote:
> Hi...
> 
> given: String of several Mb
> problem: find the lines in String containing "xyz"
> 
> 
> Idea 1:
> String.scan(/.*xyz.*/) -> ~10s runtime
> 
> Idea 2:
> String.grep(/.*xyz.*/) -> ~3s (but gives the \n too)
> 
> Idea 3:
> loop String.index("xyz",lastmatch+3)
> loop results array and grep in match area for line
> -> 0,5s

Did you try something like this?

irb(main):003:0> big_string.each do |x| puts x if x=~/xyz/ end
eeexyzfff
qqqqxyzqqq
=> "abc\neeexyzfff\naadfwe\nqqqqxyzqqq\n"
irb(main):004:0> big_string.split.grep(/xyz/)
=> ["eeexyzfff", "qqqqxyzqqq"]
irb(main):005:0>

Intuitively it seems to me that wildcards (especially unanchored) in REs
will slow them down.

 -Michael