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From: Aldric Giacomoni on 12 Mar 2010 13:54
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?
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Posted via http://www.ruby-forum.com/.

From: Chuck Remes on 12 Mar 2010 16:04
On Mar 12, 2010, at 12:54 PM, 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?

I remember reading that article when it was first published.

Ruby switched to a new regex library almost 2 years ago. Check out http://rubyforge.org/projects/oniguruma for more information.

It would be interesting to see those benchmarks run again with these new implementations.

cr


From: Siep Korteling on 12 Mar 2010 16:14
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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From: Yukihiro Matsumoto on 12 Mar 2010 17:47
Hi,

In message "Re: Ruby Regexp implementation?"
on Sat, 13 Mar 2010 03:54:09 +0900, Aldric Giacomoni <aldric(a)trevoke.net> writes:

|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?

No plan. We need more (human) resource.

matz.

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