[Pw_forum] Parallelization of diaghg

[Axel Kohlmeyer]

On 1/6/07, Alexander Shaposhnikov <shaposh at isp.nsc.ru> wrote:
>
>
> The SMP speedup for relatively large pw.x jobs (like scf calc. of 192 atom
> ZrO2 supercell with 50 ecut) is ~4.5. As i said, the cdiaghg does not
> parallelize and takes ~1/3 exec time of the whole 8-cpu job. Consider it
> could be efficiently run in parallel to get, say, 2X speedup on 8cpus - I
> could achieve ~5.5X total SMP speedup.
> Thats the difference.
>
> On the other hand, memory contention is indeed huge problem for cp/cpmd codes,
> so this Xeon machine is barely faster than dual Opteron 280 2.4GHz (4cores)
> for cpmd. For pw.x , however, it is ~2.5 faster for large jobs -and could be
> made even better with some working diaghg parallelization algorithm.

hmmmm.... what version of pw.x are you referring to?
at least in version 3.2 there should be a parallel diagonalization
that is used in pw.x (subroutine cdiagonalize in Modules/ptoolkit.f90).
as far as i understand, this is not easy to parallelize, so there
is an estimator that checks, whether the serial or the parallel algorithm
would be more efficient.

cheers,
   axel.
>
> > cheers,
> >     axel.
>
> Best Regards,
> Alexander Shaposhnikov
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>


-- 
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Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
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