The following may be of interest to anyone running NM with the Intel compiler on
an AMD or other non-Intel processor. This apparently
has come to light with Intel's recent $1.25 billion antitrust settlement to AMD
. The FTC is currently
looking into the Intel compiler issue and may require further action on Intel's
part to correct its
'defective' compiler , which deliberately cripples performance on non-Intel
chips. The
effect is fairly large - improvements of about 50% in performance are observed
with
the AMD processors when the compiler is tricked into thinking it is compiling
for an Intel processor.
See http://www.agner.org/optimize/blog/read.php?i=49 for a more complete
version - here is an excerpt:
"Many software programmers consider Intel's compiler the best optimizing
compiler on the market, and it is often the preferred compiler for the most
critical applications. Likewise, Intel is supplying a lot of highly optimized
function libraries for many different technical and scientific applications. In
many cases, there are no good alternatives to Intel's function libraries.
Unfortunately, software compiled with the Intel compiler or the Intel function
libraries has inferior performance on AMD and VIA processors. The reason is
that the compiler or library can make multiple versions of a piece of code,
each optimized for a certain processor and instruction set, for example SSE2,
SSE3, etc. The system includes a function that detects which type of CPU it is
running on and chooses the optimal code path for that CPU. This is called a CPU
dispatcher. However, the Intel CPU dispatcher does not only check which
instruction set is supported by the CPU, it also checks the vendor ID string.
If the vendor string says "GenuineIntel" then it uses the optimal code path. If
the CPU is not from Intel then, in most cases, it will run the slowest possible
version of the code, even if the CPU is fully compatible with a better version."
Robert H. Leary, PhD
Fellow
Pharsight - A Certara(tm) Company
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