From: Sean O'Halpin <sean.ohalpin@...>
Date: 2006-07-28T01:46:46+09:00
Subject: Re: String#chop slow? REALLY slow?

On 7/27/06, Mat Schaffer <schapht@gmail.com> wrote:
> I just did a quick benchmark to prove something to myself.  But I'd
> like to get a sanity check from the people on the list.
>
Using Ara's code:

Rehearsal --------------------------------------------
Indexing   0.109000   0.000000   0.109000 (  0.109000)
Chop       6.766000   8.250000  15.016000 ( 15.110000)
Chop2      2.656000   3.781000   6.437000 (  6.468000)
---------------------------------- total: 21.562000sec

               user     system      total        real
Indexing   0.156000   0.000000   0.156000 (  0.156000)
Chop       0.094000   0.000000   0.094000 (  0.094000)
Chop2      0.187000   0.000000   0.187000 (  0.187000)

> ruby -v
ruby 1.8.4 (2005-12-24) [i386-mswin32]

I think the difference in performance is because internally chop does
a dup on the string then calls chop! whereas the index operation
creates a new string which shares the old string but with a different
length. I guess this is also why the rehearsal and final results
differ - cutting out the cost of GC doesn't reflect the true cost of
using chop (especially with big strings).

Regards,
Sean