[FFmpeg-devel] [PATCH] Runtime detection for the number of processors/cores

[François Revol]

> 
> Philipp Meinen wrote:
> > Hello FFmpeg Team
> >
> > The attached patch is an attempt to allow runtime detection for the
> > number of online processors/cores instead of having to specify the
> > number of threads. The idea is to type:
> >     ffmpeg -threads 0 ....
> > to use as many threads as processors/cores are online.
> >
> > I guess cmdutils.c/h is not the right file to place the new
> > detection function. To which file should this function belong?
> >
> > Comments welcome :)
> 
> This is the wrong way to go about it.  The number of processors in 
> the
> machine is not interesting, the number of processors we're running on
> is.  On Linux, this information can be found from 
> sched_get_affinity().
> Other systems have other methods.

  _SC_NPROCESSORS_ONLN    Number of processors online

Seems to mean the same to me, unlike:

  _SC_NPROCESSORS_CONF    Number of processors configured
  _SC_NPROCESSORS_MAX     Max number of processors supported by 
platform

cf.
http://compute.cnr.berkeley.edu/cgi-bin/man-cgi?sysconf+3

But once again this only works on POSIX (might work on Haiku), but 
won't on win32 or OS/2.

Fran?ois.