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Re: tune gcc



On Mon, Mar 17, 2003 at 06:04:21PM +0200, Jerome BENOIT wrote:
> 
> 
> David Z Maze wrote:
> >Jerome BENOIT <jgmbenoit@wanadoo.fr> writes:
> >
> >
> >>I have a very naive question:
> >>Can Debian tune the GNU C Compiler ?
> >>
> >>[e.g., put `-cpu=pentium' automaticly on Pentium box]
> >
> >
> >There's a pentium-builder package that tries to do this, or you can
> >try to set CFLAGS for the program in question.   With a limited number
> >of exceptions, though, conventional wisdom is that this buys you
> >little in performance at the cost of portability of binaries to other
> >x86-based machines.
> 
> To be frank, the question arised when I read in gsl-1.3/INSTALL:
> 
> >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
> Hints for Intel (Pentium)
> ========================
> 
> For the Pentium 4 with GCC-3.2 the flags,
> 
>       CFLAGS="-O2 -march=pentium4 -mfpmath=sse -msse2"
> 
> increase performance by 33% (reported by Sam Halliday <fommil@yahoo.ie>)
> <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> 
> Since I use my Deabian box mainly to make numerical computations,
> I begin to think about these exceptions

Ah, fair enough.  Scientific libraries and crypto (OpenSSL apparently
gets a HUGE speed boost one some sparc CPU when compiled with processor
specific optimisations) are the expcetion to the rule.  Generally,
though, it doesn't gain you much :-)

-- 
Rob Weir <rweir@ertius.org>				http://ertius.org/

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