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Re: best optimization under IRIX ?
On Tue, Sep 05, 2000 at 11:38:45PM -0700, Tim Prince wrote:
> You must add -funroll-loops or -funroll-all-loops;
"-funroll-all-loops" is good for another 7% of speed up. Well,
i tried only once... "-funroll-loops" shows no effect currently.
> I usually got about 70%
> of MipsPro 7.3 Fortran speed from g77, and gcc should be closer than that to
> the speed of MipsPro C. -O3 does interprocedural analysis only in a forward
> direction within one file, while -Ofast does it it link time. Also, you
> must perform many of the usual optimizations in source code as gcc is much
> more faithful to your code.
May be. (Un-?)fortunately it's not my code :)
That does not mean that i could do it better but that i don't even try
to mess with the algorithms/ordering.
> ----- Original Message -----
> From: "Matthias Kurz" <mk@baerlap.north.de>
> > What are the optimization options that give the maximum speed on
> > a O2000/R10000 ?
> > Currently the native "cc" with "-32 -Ofast=IP27" generates code that runs
> > twice as fast as "gcc -mabi=n32 -O3 -mips3 -r4000". I see neither -mips4
> > nor -r10000 in the man page.
I'm using -n32 with cc btw. - but that's covered by -Ofast anyway.
^
(mk)
--
Matthias Kurz; Fuldastr. 3; D-28199 Bremen; VOICE +49 421 53 600 47