compiler influence question & intro

Axel akoh... at gmail.com
Wed Aug 6 17:20:18 CEST 2008



On Aug 6, 4:25 am, "Ondrej Marsalek" <ondrej.... at gmail.com>
wrote:
> hello everyone,
[...]

> someone convinces me that it is worth the extra effort needed to get
> it right. does anyone have a direct comparison of g95 and pgi cp2k
> builds on amd64 (or intel compiler on intel hw) as for overall speed?

one more remark. who says that you _have_ to use PGI on AMD
processors?
i've been using intel compilers on opterons with _very_ good results.
you have to check carefully to have a working patchlevel, but that is
independent o fhte hardware. the key to good and reliable execution
with intel
compilers is to not optimize too aggressively.
with intel 10.1 i get the best performance on DFT codes using:
-O2 -unroll -pc64 -march=pentium3 -mtune=core2
works well with both intel core2 and opteron.
please note that the default settings for intel compilers is to
optimize for pentium4 (netburst) architecture, which is a very
different beast than pentium3, opteron, and intel core.

i've seen the myth of "pgi is a must with opteron" being spread over
and over by computing center staff, but that does not translate to
applications like cp2k (or cpmd, quantum espresso and alike).

cheers,
   axel.

>
> regards,
> ondrej marsalek


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