From: Robert Klemme <shortcutter@...>
Date: 2009-02-27T23:49:32+09:00
Subject: Re: Array performance question

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2009/2/27 Jim Menard <jim.menard@gmail.com>:
> Here's a real Array performance mystery. I can't help my friend figure
> this one out. He writes,
>
> =3D=3D=3D=3D=3D=3D=3D=3D
>
> Is there a known bug in Ruby array performance? =A0I spent a lot of time
> yesterday boiling down the following example
>
>
> http://blogs.codehaus.org/people/geir/archives/001768_baffled_with_ruby.h=
tml
>
> only because I still can't believe I'm not doing something incredibly
> stupid. =A0(I'm a newbie, "Reluctant Rubyist")
>
> =A0I'm just not used to arrays behaving this way :) =A0Anyone have any
> insight?
>
> =3D=3D=3D=3D=3D=3D=3D=3D
>
> 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.

Slightly modified test (attached):

15:44:06 Temp$ ruby bm.rb bm; ruby bm.rb bmbm; ruby19 bm.rb bm; ruby19
bm.rb bmbm
1.8.7
                                    user     system      total        real
size =3D 10000 10000              0.125000   0.000000   0.125000 (  0.11400=
0)
size =3D 100000 100000            0.859000   0.000000   0.859000 (  0.86300=
0)
size =3D 1000000 1000000         24.969000   0.000000  24.969000 ( 24.96100=
0)
1.8.7
Rehearsal -----------------------------------------------------------------
size =3D 10000 10000             24.235000   0.032000  24.267000 ( 24.30800=
0)
size =3D 100000 100000           18.078000   0.000000  18.078000 ( 18.15063=
0)
size =3D 1000000 1000000         14.297000   0.000000  14.297000 ( 14.28900=
0)
------------------------------------------------------- total: 56.642000sec

                                    user     system      total        real
size =3D 10000 10000             12.031000   0.000000  12.031000 ( 12.03900=
0)
size =3D 100000 100000           10.250000   0.000000  10.250000 ( 10.29095=
0)
size =3D 1000000 1000000          8.985000   0.000000   8.985000 (  8.98900=
0)
1.9.1
                                    user     system      total        real
size =3D 10000 10000              0.016000   0.000000   0.016000 (  0.02700=
0)
size =3D 100000 100000            0.031000   0.000000   0.031000 (  0.02800=
0)
size =3D 1000000 1000000          0.047000   0.000000   0.047000 (  0.04300=
0)
1.9.1
Rehearsal -----------------------------------------------------------------
size =3D 10000 10000              0.032000   0.000000   0.032000 (  0.04300=
0)
size =3D 100000 100000            0.032000   0.000000   0.032000 (  0.04300=
0)
size =3D 1000000 1000000          0.031000   0.000000   0.031000 (  0.04300=
0)
-------------------------------------------------------- total: 0.095000sec

                                    user     system      total        real
size =3D 10000 10000              0.031000   0.000000   0.031000 (  0.03900=
0)
size =3D 100000 100000            0.047000   0.000000   0.047000 (  0.04300=
0)
size =3D 1000000 1000000          0.032000   0.000000   0.032000 (  0.04300=
0)

Strange that the rehearsal has this dramatic effect.  Normally it
should simply execute the block twice to warm up the system.

Kind regards

robert


--=20
remember.guy do |as, often| as.you_can - without end

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