From: Paul Lutus <nospam@...>
Date: 2006-08-27T20:35:11+09:00
Subject: Re: Ruby threads and the system call

Vincent Fourmond wrote:

/ ...

>   Thoughts ?

Try this code:

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

#!/usr/bin/ruby -w

system "rm temp.txt" if File.exists? "temp.txt"

10.times { |i|
   x = Thread.new(i) {
      10.times { |j|
         fork {
            system "echo #{i}, #{j} >> temp.txt"
         }
         Process::wait
      }
   }
   x.join
}

system "wc -l temp.txt" # should print "100 temp.txt"

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

According to the documentation for "fork", "Process::wait" is needed to
avoid the creation of zombie processes. "x.join" assures that the log file
isn't written by multiple processes in a way that corrupts it.

If you want to test simultaneous independent threads, you could write to a
separate file per thread, then combine the files after all threads have
completed as an accuracy check. But I don't see this as anything but
multiple writes to a single file (or console output) that creates I/O
inconsistencies, in an otherwise consistent program.

> The third behaves a little better, but
> crashes after, say, 3 to 4 system calls in a thread...

As to "crash", what error messages did you see? How do you define "crash"?

This may be system-related. You might not have the resources required for
this program, if all threads and forks run at once. Just a guess.

-- 
Paul Lutus
http://www.arachnoid.com