Re: [Gimp-developer] Ways to improve Gimp 2.9 performance

[Partha Bagchi <partha1b gmail com>]

Well, you have a point. But if you look at the documentation, it says:

-Ofast

Disregard strict standards compliance. -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math and the Fortran-specific -fno-protect-parens and -fstack-arrays. 

So, While O3 turns on -ftree-vectorize, -Ofast is not strictly compliant and turns on fast-math, I do it separately I use the above incantation.

Finally, since I compile atk/glib/pango/cairo by myself, I do use the above optimization for all the builds.

Btw, I build Gimp on Windows and Mac, so your mileage may vary.

On Sat, Mar 2, 2013 at 10:00 AM, Elle Stone <l elle stone gmail com> wrote:

On 3/2/13, Partha Bagchi <partha1b gmail com> wrote:
> I thought Gentoo was all about optimizing a linux distribution to your
> specific proecessor. :)
>
> Anyway, try the following optimization and see if it makes a difference in
> your setup:
>
> ./autogen CFLAGS="-O3 -ffast-math -ftree-vectorize" ...

Sorry! I spoke in too broad a generalization. *Most* Linux
distributions aren't optimized to a specific processor. Gentoo is set
up so you roll your own, as is Linux from Scratch (others? Arch?). The
Gentoo documentation recommends -O2 for general usage, to be on the
safe side. The Linux from Scratch article recommends -O3. Neither
article is especially new, so were written in reference to older
versions of gcc.

Probably what level of optimization does what changes as gcc changes,
but according to the gcc documentation, -Ofast includes -ffast-math
and -ftree-vectorize. Is there a reason why using "-O3 -ffast-math
-ftree-vectorize" might be better than using "-Ofast"?

Elle