Re: [Boost-users] Understanding Threads: Slow on Win32 with DLL

On Tue, Nov 30, 2010 at 4:38 PM, Simon Adler wrote: If I use all threads all four cpus are in 100% usage - they are all together

working but require more than twice the time - Yes i am sure that every thread is just working on 2500 Elements.

Hmm, are you sure of that because the different threads are all producing log output, perhaps to std::cout? I wonder if there's some unobvious shared resource (such as an ostream) that's being properly locked against concurrent access, but the locking is inducing the delay you're observing.