From: Fred Phillips <fophillips@...>
Date: 2008-08-25T03:06:48+09:00
Subject: Re: Array.shuffle/Array.shuffle!

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On Sun Aug 24 19:17:11 2008, Stefan Rusterholz wrote:

> which for many cases probably still is faster in ruby since it runs
> mainly in C, I didn't bench it, though

Seems you=E2=80=99re right:

Rehearsal -------------------------------------------------------
Knuth:               10.900000   0.000000  10.900000 ( 10.902161)
Sort by #{rand}:     11.050000   0.000000  11.050000 ( 11.060635)
--------------------------------------------- total: 21.950000sec

                          user     system      total        real
Knuth:               10.930000   0.020000  10.950000 ( 10.946718)
Sort by #{rand}:     11.020000   0.000000  11.020000 ( 11.020902)



 require 'benchmark'

 class Array
   # Shuffle the array                                                     =
     =20
   def shuffle!
     n =3D length
     for i in 0...n
       r =3D Kernel.rand(n-i)+i
       self[r], self[i] =3D self[i], self[r]
     end
     self
   end

   # Return a shuffled copy of the array                                   =
     =20
   def shuffle
     dup.shuffle!
   end
 end
=20
 n =3D 500=20
=20
 a =3D (1..10000).map { rand }
 Benchmark.bmbm(20) do |x|
   x.report("Knuth:")           { n.times { a.shuffle } }
   x.report('Sort by #{rand}:') { n.times { a.sort_by { rand } } }
 end


--=20
Fred O. Phillips
http://fophillips.org
BBC7 7572 755F 83E0 3209  504A E4F7 874F 1545 9D41

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