Re: Enabling OpenMP by default

[Thomas Weber]

On Mon, Mar 11, 2013 at 06:44:34PM +0100, c. wrote:
> 
> On 11 Mar 2013, at 01:30, address@hidden wrote:
> 
> > 
> > IMHO, it's always great to fully utilize the hardware even if it doesn't
> > lead to considerable gain in performance.
> 
> 
> I could not disagree more with this statement. It assumes no other processes 
> ever need to use your hardware concurrently, which is usually _NOT_ the case.

It assumes no such thing. It assumes that there are free CPU cycles
available on more than one core and that using those will not slow the
system down *on average*. Making a general statement here is probably
impossible, as this depends on workload, processor caches, etc.

Make no mistake: just because you are using OpenMP does not mean that
your program is exempt from the normal scheduling of the operating
system.

        Thomas