From: Robert Klemme <shortcutter@...>
Date: 2009-10-10T00:04:53+09:00
Subject: Re: Green Threads - I want them to thrash...

2009/10/9 Matt Brooks <mattbrooks@gatech.edu>:
> All Day I have tried to accomplish the following using threads, and just
> could not get it to work.  I want them to thrash back and forth having
> the power to do stuff....
>
> I want two threads to execute and fight each other to send commands to a
> unit.  With each thread they just call methods with certain arguments.
> I want them to send the commands at the same time.
>
> I guess I am realizing that isn't possible, only one will have control
> at a time, thats fine, I want them to pass control to each other
> continously, seemingly randomly to me from the outside.
>
> Also in both threads i have a forever loop.
>
> so for example
>
> a = Thread.new do
> loop do
> method that sends commands, about 60 of them
> end
> end
>
>
> b = Thread.new do
> loop do
> method that sends different commands, about 20 of them
> end
> end
>
>
>
> no matter what, thread a only runs a few commands before thead b takes
> over forever, and thread a never executes again.
>
> To combat the problem I tried doing this after the creation of the
> threads, in main I guess you call it...
>
>  loop do
>  a.priority = -1
>  b.priority = -2
>  sleep(50)
>  b.priority = -1
>  a.priority = -2
>  end
>
>
> I also tried positioning Thread.pass randomly throughout the two
> threads, hoping that would tell the thread, hey let the other guy have a
> chance, then that thread would get to his Thread.pass meaning let the
> first guy have a chance to send some stuff!!
>
> All these ways have some outcome, just the second thread executes
> forever....
>
> Any ideas, thank you very much for the help!!

You did not mention the version you are using, so I assume it was
1.8ish.  It does work on 1.9, but it takes some time:

17:00:10 desktop$ cat th.rb

require 'thread'

m = Mutex.new

(1..2).map do |i|
  Thread.new i do |ii|
    20000.times do
      m.synchronize do
        puts ii
      end
    end
  end
end.each {|th| th.join}

17:00:16 desktop$ allruby th.rb | uniq
CYGWIN_NT-5.1 padrklemme1 1.5.25(0.156/4/2) 2008-06-12 19:34 i686 Cygwin
========================================
ruby 1.8.7 (2008-08-11 patchlevel 72) [i386-cygwin]
1
2
========================================
ruby 1.9.1p129 (2009-05-12 revision 23412) [i386-cygwin]
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
1
2
17:00:20 desktop$

Kind regards

robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/