From: gabriele renzi <surrender_it@...1.vip.ukl.yahoo.com>
Date: 2004-04-21T17:14:06+09:00
Subject: Re: efficient collect+compact ?

il 21 Apr 2004 01:27:07 GMT, Martin Pirker <nospam@sbox.tu-graz.ac.at>
ha scritto::

>Hello...
>
>What's the most efficient way for
>
>puts [1,2,3,4,5,6,7,8,9,10].collect{ |x| next if x % 2 == 0; x+10 }.compact
>or
>puts [1,2,3,4,5,6,7,8,9,10].collect!{ |x| next if x % 2 == 0; x+10 }.compact!
>

try yourself:


map!+compact! 11
  0.141000   0.000000   0.141000 (  0.141000)
map+compact 21
  0.078000   0.000000   0.078000 (  0.078000)
inject    21
  0.235000   0.000000   0.235000 (  0.234000)
external  21
  0.093000   0.000000   0.093000 (  0.094000)
external for 21
  0.094000   0.000000   0.094000 (  0.094000)

# code 
require 'benchmark'
Z=(1..100000).to_a
Benchmark.bm(10) do |b|
 b.report 'map!+compact! ' do
   ary=Z.map!{ |x| next if x % 2 == 0; x+10 }.compact!
   p ary[0]
 end
 b.report 'map+compact ' do
   ary=Z.map{ |x| next if x % 2 == 0; x+10 }.compact
   p ary[0]
 end
 b.report 'inject ' do
   ary=Z.inject([]) { |s, x| x % 2 == 0 ? s : s << x + 10 }
   p ary[0]
 end
 b.report 'external ' do
   ary=[]
   Z.each {|x| ary<<(x+10) unless x%2==0 }
   p ary[0]
 end
 b.report 'external for ' do
  ary=[]
  for i in Z
   ary<<(i+10) unless i%2==0
  end
  p ary[0]
 end
end