On Mon, Aug 23, 2010 at 8:32 AM, Jeff Flinn
Mathias Gaunard wrote:
On 23/08/10 15:00, Jeff Flinn wrote:
Just beware, IIUC, that the returned count includes hyperthreads(intel). Which if used to set up a thread pool may lead to surprisingly poor performance.
What makes you think so?
Experience with our application using 2 calculation-threads on a hyperthreaded dual core was 80% faster than using 4 calculation-threads.
What makes you ask? :-)
I also have to pipe in on this, I have learned to truly *hate* the Intel hyper-threading, it hobbles my threaded programs severely, severely enough that I put in an override configuration option so the user can specify how many *real* cores they have... I still know not the purpose of them, other then to slow everything down... (Well yes I do know the purpose, but only in poorly written threaded apps anyway.)