On Wed, Jun 17, 2009 at 7:29 PM, pat eyler<pat.eyler / gmail.com> wrote:
> that's a nice article about some real-world benchmarking.  ¨Â ÷éóè
> 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 dÃÂbord ñÕdes enfants, mais peu
dÃÆntre elles sÃÆn souviennent.

All adults have been children first, but not many remember.

[Antoine de Saint-ExupñÓy]