From: Alexandre Hausen <alex.hausen@...>
Date: 2009-06-20T03:15:07+09:00
Subject: Re: String += vs <<

Classical Copy&Paste bug ;-)
Lines 8 and 14 both read "a += b" in strings.rb.
However line 14 should read "a << b".


--
Alexandre



On Jun 18, 5:08 am, Robert Dober <robert.do...@gmail.com> wrote:
> On Wed, Jun 17, 2009 at 7:29 PM, pat eyler<pat.ey...@gmail.com> wrote:
> > that's a nice article about some real-world benchmarking.  I wish
> > more people did things like this.
>
> If you search the archives you might find a certain Robert preaching,
> never to use a += b when sequences were concerned. Do I feel clever
> now? No rather stupid.
>
> Appologies for the lengthy code snippets.
>
> Although I fully acknowledge the value of the post and that it might
> be a life saver I would like to add that I pretty much have the
> feeling that immutable is preferable over mutable.
> And it seems that modern VMs (jruby, 1.9, ???)  kind of are written
> for that programming style. I am also aware that they make micro
> benchmarks like the following even less meaningless, but please
> consider it just as a Whack On The Head (nonviolently of course).
>
> ---------------------------------------------------------
> 512/19 > cat strings.rb
>
> N = 10_000
> b = "Wassitmean"
> require 'benchmark'
> Benchmark.bmbm do | bench |
>   a = "Ruby Rules Re Rowld"
>   bench.report "+=" do
>     N.times do
>       a += b
>     end
>   end
>   a = "Ruby Rules Re Rowld"
>   bench.report "<<" do
>     N.times do
>       a += b
>     end
>   end
> end
>
> 513/20 > jruby -v strings.rb
> jruby 1.3.0 (ruby 1.8.6p287) (2009-06-06 6586) (OpenJDK Client VM
> 1.6.0_0) [i386-java]
> Rehearsal --------------------------------------
> +=   1.256000   0.000000   1.256000 (  1.191000)
> <<   9.384000   0.000000   9.384000 (  9.384000)
> ---------------------------- total: 10.640000sec
>
>          user     system      total        real
> +=  23.397000   0.000000  23.397000 ( 23.397000)
> <<  52.953000   0.000000  52.953000 ( 52.953000)
>
> ruby 1.9.1p129 (2009-05-12 revision 23412) [i686-linux]
> Rehearsal --------------------------------------
> +=   0.360000   0.020000   0.380000 (  0.406038)
> <<   1.040000   0.130000   1.170000 (  1.209839)
> ----------------------------- total: 1.550000sec
>
>          user     system      total        real
> +=   1.770000   0.230000   2.000000 (  2.056577)
> <<   2.410000   0.240000   2.650000 (  3.456429)
>
> I believe that I hit the GC in JRuby with the default settings and the
> above might be an indication how performing
> the short time object allocation is nowadays. Ruby1.9 has enough
> memory on my machine to be that fast but still += is faster than <<.
>
> Cheers
> Robert
>
> --
> Toutes les grandes personnes ont d’abord été des enfants, mais peu
> d’entre elles s’en souviennent.
>
> All adults have been children first, but not many remember.
>
> [Antoine de Saint-Exupéry]