[Wien] k point parallel mode

[Laurence Marks]

A comment on Peter''s comment. OMP_NUM_THREADS might have an effect,
but the parameter is really MKL_NUM_THREADS if you are using Intel's
mkl library -- and even then the compiler makes it's own decisions
about how many it will use and this varies with version of the
compiler (and probably what one has to set).

Also...many of these things depend upon exactly what is in your
computer, e.g. memory speed, bus speed as well as what else is
running. Best is to do your own benchmarks, e.g. see
http://www.wien2k.at/reg_user/benchmark/. For instance, while on older
computers Intel's hyperthreading was not good much to my surprise when
I tried it (by accident) on a recent dual hex-core machine it was
quite reasonable.

N.B., the same holds for mpi -- very hardware and software dependent
in my experience.

On Fri, Dec 30, 2011 at 5:44 AM, Peter Blaha
<pblaha at theochem.tuwien.ac.at> wrote:
>> To "make" the file, you use an editor (nothing more or less) and putthe
>> file in the directory where you are running the job. I have notlooked, but
>> there is probably something in w2web to do this.
>> N.B., the code does not use OMP anywhere (at present) so this will notdo
>> anything.
>
>
> Just a small correction: If you are using the mkl, OMP_NUM_THREADS will have
> an
> effect in the diagonalization part of lapw1 (which is often the main part
> anyway).
>
> However, while OMP_NUM_THREADS = 2 is quite effective and speeds up the
> diagonalization
> significantly, =4 is far less efficient and = 6 is usually useless.
>
> PS: On a 6 core machine you should run ONLY 6 jobs at the same time (or 3
> k-parallel
> jobs with OMP_NUM_THREADS=2) !!!
> Intels "hyperthreading", which mimics "12 processors" to you, should even be
> switched
> off (BIOS), because it will slow down the jobs.
>
>
>
> --
> -----------------------------------------
> Peter Blaha
> Inst. Materials Chemistry, TU Vienna
> Getreidemarkt 9, A-1060 Vienna, Austria
> Tel: +43-1-5880115671
> Fax: +43-1-5880115698
> email: pblaha at theochem.tuwien.ac.at
> -----------------------------------------
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu 1-847-491-3996
"Research is to see what everybody else has seen, and to think what
nobody else has thought"
Albert Szent-Gyorgi