From: Erik Veenstra <erikveen@...>
Date: 2008-10-07T05:58:01+09:00
Subject: Re: Concurent (using threads) slower than sequential -doubt

If you are on Linux, you might want to have a look at the gem
"forkandreturn" [1]. ForkAndReturn handles each element in an
enumeration in a seperate process [2].

gegroet,
Erik V. - http://www.erikveen.dds.nl/

[1] http://www.erikveen.dds.nl/forkandreturn/doc/index.html

[2] ...if you're on a multicore machine. Oops. Will be fixed in
the next release.

----------------------------------------------------------------

 $ cat count1.rb
 files   = ["numbers0.txt", "numbers1.txt", "numbers2.txt"]
 result  = 0

 files.collect do |file|
   res   = 0

   File.open(file) do |file|
     file.each do |line|
       res += line.to_i
     end
   end

   res
 end.each do |res|
   result += res
 end

 p result

----------------------------------------------------------------

 $ diff -ur count[12].rb | clean_diff
 +require "forkandreturn"
 +
  files   = ["numbers0.txt", "numbers1.txt", "numbers2.txt"]
  result = 0

 -files.collect do |file|
 +files.concurrent_collect do |file|
    res  = 0

    File.open(file) do |file|

----------------------------------------------------------------

 $ time ruby count1.rb
 81627450482688

 real    0m15.309s
 user    0m15.201s
 sys     0m0.076s

----------------------------------------------------------------

 $ time ruby count2.rb
 81627450482688

 real    0m8.976s    <=== Multicore!
 user    0m17.177s   <=== Multicore!
 sys     0m0.204s

----------------------------------------------------------------

 $ uname -a
 Linux laptop 2.6.24-19-generic #1 SMP Wed Aug 20 22:56:21 UTC 2008
i686 GNU/Linux

----------------------------------------------------------------

 $ ruby --version
 ruby 1.8.6 (2008-06-20 patchlevel 230) [i686-linux]

----------------------------------------------------------------

 $ gem list | grep -ie forkandreturn
 forkandreturn (0.2.0)

----------------------------------------------------------------