Re: [proaudio] gcc cflags

[Dominique Michel <dominique.michel@xxxxxxxxxxxx>]

Thank you,
The vectorize flags are for loop optimisation. I read on the IBM website
at they can increase the speed of a program by a factor of 20. But I
read in another website at all depend of the size of the loop, because
they append additional structure control to the code, and at in case of
small loops, those additional structures will do the resulting program
slower.

I think at it will be a good flag to have with math intensive programs
as multimedia programs, but I am not sure at it is a good flag to have
as a system flag. Do you know something about this issue?

On Wed, 23 Aug 2006 16:20:18 -0500
"Reuben Martin" <reuben.m@xxxxxxxxx> wrote:

> Based on how agressive you seem to want to be, I would recommend:
> 
> CFLAGS="-O2 -march=pentium4 -pipe -ftracer -fweb -ftree-vectorize"
> 
> The -ftree-vectorize does wonders.
> 
> If you are still feeling like you want to push it a little harder you
> can try changing -O2 to -O3 and adding -ffast-math. Some things don't
> work well with -O3 though (some of the LADSPA plugins don't work right
> with -O3) and some programs don't work correctly with -ffast-math.
> (for instance OpenOffice will fail to compile if Python has been built
> with -ffast-math turned on)
> 
> -Reuben
> 

I don't use -ffast-math and don't want it. I have no problem at this
time with -O3 and -fforce-addr, and that even to compile the LADSPA
plugin or openoffice. The only problem is at the resulting code is
bigger as with -O2 alone and at it seam to be not faster. I
try to remove the -fforce-addr and tested it with the nec2 antenna
simulation software. It was faster as with -O2 alone, but I get wrong
simulation results in some cases. So I thing at I will get with -O2 in
the future, -O3 is not a good option is you have to remove the speed
benefice of that option in order to get a correct code with all the
programs. And I don't have the time to test my flags with every one
program that I want to install.

Cheers,
Dominique