From: Robert Dober <robert.dober@...>
Date: 2007-08-24T17:19:09+09:00
Subject: Re: something I just found out, am sharing (:newbish)

On 8/24/07, Simon Schuster <significants@gmail.com> wrote:
> 075:0> a = "hello"
> "hello"
> 076:0> a += " there."
> "hello there."
> 077:0>
>
>
> neat!
not really :(
a += " there" is
a = a + " there"

a << " there"

I might be accused of premature optimizationism (A word I just made
up, I have to make an ECR ;).
But seriously there is just no need to pay the cost of the
construction of another String / Array.
Performance difference is already enormous for moderately long strings :

511/11 > cat costs.rb
# vim: sw=2 sts=2 ft=ruby expandtab tw=0:
require 'benchmark'

N = ARGV.first.to_i
a = "Hello Nice Little "
Benchmark.bmbm do
  |mybench|
  mybench.report(" += "){ N.times{ a += "." } }
  mybench.report(" << "){ N.times{ a << "." } }
end # Benchmark.bmbm do

robert@PC:~/log/ruby/ML 10:17:57
512/12 > ruby costs.rb 1000
Rehearsal ----------------------------------------
 +=    0.000000   0.000000   0.000000 (  0.002936)
 <<    0.000000   0.000000   0.000000 (  0.001008)
------------------------------- total: 0.000000sec

           user     system      total        real
 +=    0.000000   0.010000   0.010000 (  0.080035)
 <<    0.000000   0.000000   0.000000 (  0.000927)
robert@PC:~/log/ruby/ML 10:18:04
513/13 > ruby costs.rb 10000
Rehearsal ----------------------------------------
 +=    0.160000   0.020000   0.180000 (  0.565431)
 <<    0.010000   0.000000   0.010000 (  0.012393)
------------------------------- total: 0.190000sec

           user     system      total        real
 +=    0.730000   0.050000   0.780000 (  0.826307)
 <<    0.010000   0.000000   0.010000 (  0.013734)
robert@PC:~/log/ruby/ML 10:18:08
514/14 > ruby costs.rb 20000
Rehearsal ----------------------------------------
 +=    0.620000   0.010000   0.630000 (  0.741340)
 <<    0.030000   0.000000   0.030000 (  0.077221)
------------------------------- total: 0.660000sec

           user     system      total        real
 +=    3.060000   0.000000   3.060000 (  3.131026)
 <<    0.030000   0.000000   0.030000 (  0.076420)
robert@PC:~/log/ruby/ML 10:18:20
515/15 > ruby costs.rb 30000
Rehearsal ----------------------------------------
 +=    1.380000   0.020000   1.400000 (  1.452444)
 <<    0.040000   0.000000   0.040000 (  0.087939)
------------------------------- total: 1.440000sec

           user     system      total        real
 +=    6.760000   0.040000   6.800000 (  6.848208)
 <<    0.040000   0.000000   0.040000 (  0.036871)

Cheers
Robert
>
>


-- 
I'm an atheist and that's it. I believe there's nothing we can know
except that we should be kind to each other and do what we can for
other people.
-- Katharine Hepburn