From: Siep Korteling <s.korteling@...>
Date: 2010-03-13T06:14:29+09:00
Subject: Re: Ruby Regexp implementation?

Aldric Giacomoni wrote:
> This probably doesn't belong in Ruby Core. I was reading this article:
> http://swtch.com/~rsc/regexp/regexp1.html
> http://swtch.com/~rsc/regexp/regexp2.html
> http://swtch.com/~rsc/regexp/regexp3.html
> 
> And in the first few lines of the first page, it shows that the Regexp
> implementation for Perl is absolutely terrible, and it says that Ruby is
> "the same" or at least similar. Is Ruby 1.8 / 1.9 using the Thompson NFA
> matching? Will Ruby 2.0 use it?

def pathologicalize (str,  n)
  tmp = str[0]*n
  [str*n + tmp, tmp]
end

puts RUBY_VERSION
1.step(101, 10) do |n|
  full_str, part_str = pathologicalize("a?",  n)
  start = Time.now
  1000.times do
    full_str =~ /#{part_str}/
  end
  duration = Time.now-start
  puts "#{n}:\t#{duration}"
end

#output
1.9.1
1:  0.015625
11:  0.015625
21:  0.015625
31:  0.03125
41:  0.03125
51:  0.046875
61:  0.046875
71:  0.046875
81:  0.0625
91:  0.0625
101:  0.078125

Siep
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