[FFmpeg-devel] [PATCH]Use -parallel when compiling with icc

[Carl Eugen Hoyos]

Reimar D?ffinger <Reimar.Doeffinger <at> stud.uni-karlsruhe.de> writes:

> > > > +  # Use -parallel option, as recommended by Intel, but keep quiet
> > > > about it
> > > > +  check_cflags -parallel
> > > > +  check_cflags -par-report=0
> > > > +  check_ldflags -parallel
> > > >  fi
> > > 
> > > What effect does that flag have?
> > 
> > (From man icc)
> > It enables the auto-parallelizer to generate multi-threaded code for loops
> > that can be safely executed in parallel.
> 
> You should _very_ carefully benchmark that. It is not unlikely to slow
> things down, at least when used globally.

Have you any suggestions on what to test?
I was not able to see any slowdown, and both the manual and the optimization
guide (that do mention the possible slowdown of -O3) do not warn of any negative
effects.

Carl Eugen