[Llvm-bgq-discuss] QPX clang BGQ

[Hornung, Rich]

Folks,

I have recently taken Hal's latest compiler updates (version
r176829-20130309) out for a spin on a suite of loop kernels I have
developed for checking compiler optimizations.  What I found is that when
using the -ffast-math option, my result checksums are very different from
when I do not use -ffast-math (for all 30 loops in the suite except one).
An earlier version (r176751-20130307) does not show these differences.
Also, I did not see any significant performance differences across the
loop suite between these compiler versions.  For completeness, I also
compared the checksums generated when the code was compiled with the xlc
12.1 compiler.  The checksums for -O0 vs. -O3 -qnostrict vs. -O3 -qstrict
are all essentially the same.  From this I concluded that something is
broken in the latest version of the optimizer.

So, if you're going to use the latest compiler version, make sure you
check your answers.

--Rich





On 5/8/13 9:42 AM, "Jeff Hammond" <jhammond at alcf.anl.gov> wrote:

>(copying LLVM discuss - you should sign up for this list)
>
>Hi Ivo,
>
>I don't know the answer, but if you're on BGQ, you should use Hal's
>version of LLVM anyways because I think it has other important
>patches, not just QPX ones.
>
>Best,
>
>Jeff
>
>2013/5/8 Ivo Kabadshow <i.kabadshow at fz-juelich.de>:
>> Jeff,
>>
>>  does clang work with QPX on BGQ or do I need Hals clang version?
>>
>> Best
>>  Ivo
>>
>>
>> 
>>-------------------------------------------------------------------------
>>-----------------------
>> 
>>-------------------------------------------------------------------------
>>-----------------------
>> Forschungszentrum Juelich GmbH
>> 52425 Juelich
>> Sitz der Gesellschaft: Juelich
>> Eingetragen im Handelsregister des Amtsgerichts Dueren Nr. HR B 3498
>> Vorsitzender des Aufsichtsrats: MinDir Dr. Karl Eugen Huthmacher
>> Geschaeftsfuehrung: Prof. Dr. Achim Bachem (Vorsitzender),
>> Karsten Beneke (stellv. Vorsitzender), Prof. Dr.-Ing. Harald Bolt,
>> Prof. Dr. Sebastian M. Schmidt
>> 
>>-------------------------------------------------------------------------
>>-----------------------
>> 
>>-------------------------------------------------------------------------
>>-----------------------
>
>
>
>-- 
>Jeff Hammond
>Argonne Leadership Computing Facility
>University of Chicago Computation Institute
>jhammond at alcf.anl.gov / (630) 252-5381
>http://www.linkedin.com/in/jeffhammond
>https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond
>ALCF docs: http://www.alcf.anl.gov/user-guides
>_______________________________________________
>llvm-bgq-discuss mailing list
>llvm-bgq-discuss at lists.alcf.anl.gov
>https://lists.alcf.anl.gov/mailman/listinfo/llvm-bgq-discuss