From: brabuhr@...
Date: 2009-06-09T04:54:37+09:00
Subject: Re: How to sort array ascending, except zero ?

On 6/8/09, Robert Klemme <shortcutter@googlemail.com> wrote:
> On 08.06.2009 20:55, brabuhr@gmail.com wrote:
>> Assuming a stable sorting algorithm, sort twice is an option:
>>
>> irb(main):001:0> [1, 0].sort.sort_by{|n| n.zero? ? 1 : 0}
>> => [1, 0]
>
> Sorting twice only to make the block to sort simpler does not sound like
> a good operation.

Especially the to_s version :-)

Error: Your application used more memory than the safety cap of 500m.
Specify -J-Xmx####m to increase it (#### = cap size in MB).
Specify -w for full OutOfMemoryError stack trace

require 'benchmark'
Infinity = 1.0/0.0
Benchmark.bm(25) do |b|
  a = (1..500000).map{|n| rand(10) - 20}
  b.report("A")    {
    a.sort.sort_by{|n| n.zero? ? 1 : 0}
  }
  b.report("B") {
    a.sort_by {|x| x == 0 ? Infinity : x }
  }
  b.report("C") {
    max = a.max + 1
    a.sort_by {|x| x == 0 ? max : x }
  }
  b.report("D") {
    tmp = a.partition{|x| x != 0 }
    tmp[0].sort + tmp[1]
  }
  b.report("E") {
    a.sort do |x,y|
      case
      when x == 0 then  1
      when y == 0 then -1
      else x <=> y
      end
    end
  }
end

Linux 2.6.28-11-generic #42-Ubuntu SMP Fri Apr 17 01:57:59 UTC 2009
i686 GNU/Linux

ruby 1.8.7 (2008-08-11 patchlevel 72) [i486-linux]
                               user     system      total        real
A                          1.070000   0.160000   1.230000 (  1.320943)
B                          1.290000   0.140000   1.430000 (  1.691468)
C                          1.530000   0.200000   1.730000 (  2.863440)
D                          0.750000   0.180000   0.930000 (  1.323304)
E                          3.840000   0.400000   4.240000 (  5.043411)

ruby 1.9.0 (2008-06-20 revision 17482) [i486-linux]
                               user     system      total        real
A                          0.470000   0.020000   0.490000 (  0.522487)
B                          0.550000   0.010000   0.560000 (  0.631449)
C                          0.640000   0.000000   0.640000 (  0.692639)
D                          0.230000   0.020000   0.250000 (  0.279466)
E                          0.820000   0.000000   0.820000 (  0.870455)

jruby 1.3.0 (ruby 1.8.6p287) (2009-06-03 5dc2e22) (OpenJDK Client VM
1.6.0_0) [i386-java]
                               user     system      total        real
A                          1.664000   0.000000   1.664000 (  1.617000)
B                          2.315000   0.000000   2.315000 (  2.316000)
C                          2.536000   0.000000   2.536000 (  2.536000)
D                          0.772000   0.000000   0.772000 (  0.772000)
E                          5.175000   0.000000   5.175000 (  5.175000)