From: Vincent Fourmond <vincent.fourmond@9online.fr>
Date: 2006-08-27T17:17:07+09:00
Subject: Ruby threads and the system call

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  Hello !

  I've recently had quite a fair bit of trouble with Ruby threads (on a
Linux box). I wrote three different programs (attached) that write
numbers from within threads:

  * one with a standard puts
  * one with a system "echo ..."
  * one with a fork do system "echo ..." end

  The first one behaves as expected (although the numbers are perfectly
ordered, which looks suspicious). In the second one, ruby never manages
to make a second system call in a thread (and finishes before the
subprograms are terminated). The third behaves a little better, but
crashes after, say, 3 to 4 system calls in a thread...

  Is this true on other boxes ? Is it a flaw of my understanding of
threads, or a limitation inherent to the way threads are coded in Ruby ?
If that is so, it's really annoying - no way to delegate heavy tasks to
other well-written programs...

  Thoughts ?

	Vince

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#!/usr/bin/ruby

10.times do |i|
  Thread.start(i) do |i| 
    10.times do |j|
      puts "#{i}.#{j}"
    end
  end
end


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#!/usr/bin/ruby

10.times do |i|
  Thread.start(i) do |i| 
    10.times do |j|
      system "echo #{i}.#{j} "
    end
  end
end


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#!/usr/bin/ruby

10.times do |i|
  Thread.start(i) do |i| 
    10.times do |j|
      fork do
        system "echo #{i}.#{j} "
      end
    end
  end
end


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