Re: Threads: better condition variables?

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-08-10 16:41:47

--- In boost_at_[hidden], jpanzer_at_n... wrote:
> jsiek_at_l... wrote:
> 
> > William Kempf writes:
> >  > I wouldn't attach it to the condition, however.  I'd pass the
> >  > predicate into the wait.  Thus the condition can be used to 
track
> >  > different criteria.
> >  >
> >  >    cond.wait((free1 > 10)(a));
> >
> > Why would you want to use the same condition variable with 
different
> > criteria? (why not just use a different condition variable)
> 
> Example: Bounded queue.  Producer thread adds an item only if
> the queue size is less than 100, else it waits.  Consumer removes
> an item only if the queue size is greater than 0, else it waits.  
Two
> different conditions, both of them dependent on the same
> variable.
> 
> (Of course the producer also needs to be able to specify a timeout.)

This can be implemented with either one condition using multiple 
criteria or two conditions.  There isn't really an example (at least 
that I can think of) where one or the other is the only solution.  
The question is, which is the better solution for the specific 
problem.

William Kempf