[Pw_forum] Pentium-M versus Itanium

Axel Kohlmeyer akohlmey at cmm.chem.upenn.edu
Thu Mar 13 21:11:24 CET 2008

On Thu, 13 Mar 2008, Miguel Martínez Canales wrote:

MMC> Dear all,

dear miguel,

a couple of comments:

MMC> Laptop:
MMC>    example01
MMC> real	1m44.686s
MMC> user	1m41.374s
MMC> sys	0m1.864s
MMC>    example05
MMC> real	0m8.411s
MMC> user	0m7.828s
MMC> sys	0m0.140s

those examples make bad benchmarks. 
they compute too little, what you are mostly
seeing is the time to write the output... :)


MMC> Big Bad Itanium
MMC>    example01
MMC> real	1m48.417s
MMC> user	2m15.136s
MMC> sys	0m6.756s
MMC>    example05
MMC> real	0m13.028s
MMC> user	0m12.775s
MMC> sys	0m0.627s
MMC> Is it normal that user time > real time even when I am running pw.x as 
MMC> mpirun -np 1 pw.x? Is it normal that my almost 4 year old laptop running a 

as of version 10, MKL defaults to automatically switching to
multi-threaded at its own whim (see docs) unless you tell it
to run serially. hence the user time increase.

MMC> bloated distro is running the examples clearly faster than an Itanium 
MMC> machine? I swear I haven't used fancy flags anywhere, other than the 
MMC> default ones. I will also run espresso on an opteron machine, to see the 
MMC> results.

you'll have to run an input that at least stays on the CPU for
something of the order of 10mins to get some realistic numbers.


MMC> Regards,
MMC> Miguel
MMC> PS: I also swear that the very same Itanium machine used to run twice as 
MMC> fast as the same laptop, although the free FORTRAN compilers have changed a 
MMC> lot in the last couple of years.

Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
If you make something idiot-proof, the universe creates a better idiot.

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