[CIG-SEISMO] SPECFEM3D_GLOBE - Default xlf compiler flags

Dimitri Komatitsch komatitsch at lma.cnrs-mrs.fr
Sat May 19 10:07:31 PDT 2012

Hi Elliott,

Thanks for this bug report. I have just fixed that and updated the 
manual accordingly. Thus you can run 'svn update'.

Best regards,

On 04/05/2012 09:02 PM, Elliott Sales de Andrade wrote:
> Hi SPECFEM3D_GLOBE developers,
> I had a little trouble with the default compiler flags for the IBM xlf
> compiler, and I think this info might be useful for others.
> According to the manual, `FLAGS_NO_CHECK` is for fast, production code,
> but the xlf flags include -qinitauto=7FBFFFFF and
> -qflttrap=overflow:zerodivide:invalid:enable. The first one isn't so
> bad, but the second causes the binaries to run 4 times slower on our
> cluster. As no other compilers seem to have similar options enabled, I'd
> guess these were left here by accident.
> Also, on our cluster, the linking step does *not* use the GNU ld linker
> but the native AIX linker. (FYI, the manual is mistaken; it is ld that
> does the final linking, not gcc.) This AIX linker does not seem to
> understand -relax (and appears to interpret it as some other options)
> and produces unusable binaries. It would probably be helpful if this
> little gotcha was mentioned in the manual, or perhaps moved into the
> BlueGenes-specific section.
> On a side note, the manual suggests to modify the generated Makefile to
> experiment with different compiler flags. Now that the source files have
> been split into several directories, this method may be a bit tedious
> and error-prone. It would be easier to just run ./configure
> FLAGS_CHECK="options" FLAGS_NO_CHECK="other options".

Dimitri Komatitsch - komatitsch aT lma.cnrs-mrs.fr
CNRS Research Director (DR CNRS), Laboratory of Mechanics and Acoustics,
UPR 7051, Marseille, France    http://komatitsch.free.fr

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