Re: [boost] Re: Boost threads library, waiting on multiple conditions

From: David Abrahams (david.abrahams_at_[hidden])
Date: 2001-10-12 11:12:51

I know the question came up earlier about doing this on Unix with signal. In
fact, I have successfully implemented cross-platform message queueing code
which uses signal on Linux and WaitForMultipleObjects on Win32... so I know
that it can be done.

-Dave

===================================================
  David Abrahams, C++ library designer for hire
 resume: http://users.rcn.com/abrahams/resume.html

        C++ Booster (http://www.boost.org)
          email: david.abrahams_at_[hidden]
===================================================

----- Original Message -----
From: "Carl Daniel" <cpdaniel_at_[hidden]>
To: <boost_at_[hidden]>
Sent: Friday, October 12, 2001 10:58 AM
Subject: Re: [boost] Re: Boost threads library, waiting on multiple
conditions

>
> ----- Original Message -----
> From: <helmut.zeisel_at_[hidden]>
> To: <boost_at_[hidden]>
> Sent: Thursday, October 11, 2001 11:39 PM
> Subject: [boost] Re: Boost threads library, waiting on multiple conditions
>
>
> > --- In boost_at_y..., mf_dylan_at_y... wrote:
> >
> > > One thing though, how would I go about waiting on multiple
> > > conditions?  This is actually the norm in much of my multi-thread
> > > work...most of the time is spending waiting on various threads and
> > > conditions, usually one of them is a "shutdown" event, another is a
> > > checking for work to do etc. etc.
> > >
> >
> > I do not understand completely:
> >
> > When you do the same work on every condition,
> > why do you use different conditions?
> >
> > When you do different work on each condition,
> > why don't you use for every condition
> > a specfic worker thread that waits for only one condition?
> >
>
> Conservation of worker threads (which translates to a decrease in working
set and a decrease in context switches).
> Since Win32 lets one wait on (at least) 64 objects simultaneously, it's
frequently more efficient to use one (or a few
> threads) to service a large number of events.  WaitForMultipleObjects also
lets the caller specify whether to wait for
> any of the objects or to wait until all are signaled simultaneously.  The
latter behavior is rarely used, but difficult
> to simulate when not available.  In the former case, the value returned
from the call indicates which object was
> signalled.
>
> For example, a single call to MsgWaitForMultipleObjectEx can
simultaneously wait for:
> - Windows messages
> - Timeout
> - APCs
> - 60+ other objects (threads, events, mutexes, etc).
>
> Without a similar capability, there are Windows applications which will
never use boost::threads that otherwise would.
>
> -cd
>
>
> Info: http://www.boost.org  Unsubscribe:
<mailto:boost-unsubscribe_at_[hidden]>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>