Re: Lowering compiler optimisation with Apple gcc

["Jason Martin" <jason.worth.martin@gmail.com>]

I've had excellent luck on my Core 2 Mac with the latest version of gcc using

  CFLAGS="-m64 -fast"

I've also ported and optimized GMP for Core 2 Macs, and using my port
of GMP I get Pari benchmarks on my Mac Pro that out perform all of the
Opteron machines I have access to.  For details, see my website (in my
signature).

I have not encountered any "bugs" in Apple's gcc, but I have
encountered "frustrations" because the Apple gcc options are not
compatible with the Linux options that I'm familiar with.

One subtle point of building for Core 2 Macs is that current versions
of the autoconf tools do not correctly detect the CPU type.  This is
because the "uname -m" command returns the rather unhelpful "i386"
rather than the "x86_64" that one might expect.  So, you have to
manually detect the CPU (Agner Fog has some nice routines for this).

I have not tried building on the 32bit or PowerPC Macs because I don't
have access to any.

--jason

-----------------------------------------------------------
Jason Worth Martin
Asst. Prof. of Mathematics
James Madison University
http://www.math.jmu.edu/~martin
phone: (+1) 540-568-5101
fax: (+1) 540-568-6857

"Ever my heart rises as we draw near the mountains.
There is good rock here." -- Gimli, son of Gloin


On 12/15/06, Bill Allombert <Bill.Allombert@math.u-bordeaux1.fr> wrote:
> Hello PARI-dev,
>
> we regurlarly get bug reports about random problems on Apple platform,
> see #504, #523,
> <http://pari.math.u-bordeaux.fr/archives/pari-dev-0603/msg00003.html>
> <http://pari.math.u-bordeaux.fr/archives/pari-dev-0606/msg00004.html>
> and others.
>
> Unfortunately we never have been able to reproduce any of them and
> they looks like compilers bugs in various Apple gcc build.
>
> Maybe we should lower the default optimisation level to reduce breakage.
> Advanced users could still pick higher optimisation level.
>
> We could check the gcc version for the string 'Apple'.
>
> What do you think ?
>
> Cheers,
> Bill