From: Thomas Enebo <Thomas.Enebo@...>
Date: 2009-03-10T23:01:02+09:00
Subject: Re: Array performance question

Jim Menard wrote:
> Here's a real Array performance mystery. I can't help my friend figure
> this one out. He writes,
>
> ========
>
> Is there a known bug in Ruby array performance?  I spent a lot of time
> yesterday boiling down the following example
>
>
> http://blogs.codehaus.org/people/geir/archives/001768_baffled_with_ruby.html
>
> only because I still can't believe I'm not doing something incredibly
> stupid.  (I'm a newbie, "Reluctant Rubyist")
>
>  I'm just not used to arrays behaving this way :)  Anyone have any
> insight?
>
> ========
>
> He'd love a response in his blog, but with permission I'll copy
> answers here over there. He's not a regular ruby-talk reader...yet.
>
> Jim
>   
I am betting Ryan is right about GC issues.   JRuby does not fall down 
doing this either (which probably also backs up the GC theory):

ruby ~/jruby/scripts/arr_ben.rb
size = 10000 10000
  0.050000   0.000000   0.050000 (  0.057190)
size = 100000 100000
  0.660000   0.000000   0.660000 (  0.672178)
size = 1000000 1000000
 34.430000   0.340000  34.770000 ( 35.562454)

jruby --server ~/jruby/scripts/arr_ben.rb
size = 10000 10000
  0.372000   0.000000   0.372000 (  0.266000)
size = 100000 100000
  0.099000   0.000000   0.099000 (  0.099000)
size = 1000000 1000000
  0.154000   0.000000   0.154000 (  0.154000)

-Tom