From: Robert Klemme <bob.news@...>
Date: 2004-05-06T06:23:57+09:00
Subject: Re: signaling another thread


"Ara.T.Howard" <ahoward@fattire.ngdc.noaa.gov> schrieb im Newsbeitrag
news:Pine.LNX.4.44.0405051113590.30055-100000@fattire.ngdc.noaa.gov...
> On Thu, 6 May 2004, Joel VanderWerf wrote:
>
> > Ara.T.Howard wrote:
> > >
> > > what is is the prefered method in which one thread can 'signal'
another thread
> > > on some condition?  Observable?  other?
> >
> > One way is to use Thread#raise:
> >
> > $ cat thread-signal.rb
> >    class PayAttention < Exception; end
> >
> >    other = Thread.new do
> >      i=0
> >      begin
> >        loop do
> >          sleep 1
> >          i += 1 # important work
> >        end
> >      rescue PayAttention
> >        puts i
> >        retry if i < 10
> >      end
> >    end
> >
> >    watch = Thread.new do
> >      loop do
> >        sleep 3
> >        other.raise PayAttention
> >      end
> >    end
> >
> >    other.join
> >
> > $ ruby thread-signal.rb
> > 2
> > 4
> > 6
> > 8
> > 10
> > $
>
> nice - i'll take it.  thanks.

It depends on the situation: if the thread to notify may be idle, a
ConditionVariable is better.

see:
http://www.ruby-doc.org/docs/rdoc/1.9/classes/ConditionVariable.html
http://www.rubygarden.org/ruby?MultiThreading

That spares you the sleeping and is the more natural and resource saving
approach.

Regards

    robert