Re: [Boost-users] Boost semaphore with condition variable

21 Nov 2007

      On Wed, 21 Nov 2007 23:25:36 +0100, Fabian Sturm wrote:
...
This works fine and A will wait until the result is available and it
doens't matter if it starts waiting before or after B finished
calculaating.
But the problem now is that B also needs to wait for A to reach the
point in execution.
Why not do this:

void threadB()
{
  g_value = do_my_expensive_calc();
  barrier2.wait(); // start waiting *after* calculation is done
}

void threadA()
{
  barrier2.wait();
  // now can read value
  do_something_with_value(g_value)
}

Then thread B can calculate without waiting for thread A but neither 
thread will exit until they both reach the barrier.

-- 
Sohail Somani
http://uint32t.blogspot.com