[Pw_forum] parallelization issues

Stefano de Gironcoli degironc at sissa.it
Thu Mar 5 09:45:05 CET 2009

It means that since very little communication is needed across different 
images this parallelization does not suffer much (at all) if the 
communication network is not very fast... however it does not 
distribute  the memory and I/O ... which may be bad for the efficiency 
of the calculation as we are learning these days from the discussion 
going on on pool parallelization (which also is less-communication and 
more-memory&I/O intensive than R&G parallelization)...
My today understanding of this is that one could increase the number of 
processors using R&G parallelization as far as the network at hand 
allows to get a good scaling... then one can increase further the number 
of processors by adding pool parallelization and, in case of  NEB 
calculations, some image parallelization.

Hope this helps,
  Stefano de Gironcoli

Mahmoud Payami wrote:
> Dear ALL,
> In sec. of "parallelization issues" of UG, is mentioned that: "As a 
> general rule, image parallelization may give good scaling..."
> Could anybody please explain what exactly it means in terms of say, 
> static linking, using more npools, or so.
> Bests,
>            Mahmoud Payami
> Physics Group, AEOI.
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