[Omp] OpenMP with different compilers

[Dieter an Mey]

In fact we have made similar experiences, that it was hard to achieve 
any speedup on an Altix system using the Intel C++ compiler V8.1, 
whereas the same code compiled with the same compiler scaled much better 
on an Opteron system.
My guess is that it has to do with the operating environment, total load 
of the machine etc. and not so much with complation and optimization by 
the compiler.

regards
Dieter


Nils Smeds wrote:

> 
> xxd104 at gmail.com said:
> 
>>Intels- ifort is 3-4 times slower than g77.
> 
> 
> Specific claims such as the one above should in my opinion include a URL
> pointer to the full report with run times, compiler and linker options used,
> compiler versions used and preferably source code and sample input files. 
> 
> A second thing to keep in mind is that this particular comparison used the 
> Intel compiler on AMD Opteron (x86_64). Were you using the EM64T version of 
> the compiler? Were you using it in a way that generated x86_64 instructions?
> 
> /Nils


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Dieter an Mey
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