[Q-e-developers] Band parallelization

[Paolo Giannozzi]

On Mon, 2013-06-17 at 16:30 +0200, nicola varini wrote:

> Paolo, what kind of material do you think is useful to have? 
> A tutorial or a user guide or some guidelines?

as a first approximation, any kind of material. There is
nothing (rien nichts niente nada ничего موشي ) right now 
in the documentation. There is just a single mention of 
option "-nband" or "-nb" in Doc/user_guide.tex, and this
mention in PW/examples/EXX_example/README:
  An experimental parallelization on the band structure
  is also available (pw.x -nbgrp N)
My specidic original motivation for my question is to 
figure out what the "smallmem" option exactly does and 
in which cases the distribution of arrays dimensioned 
(nkb,nbnd) hidden in "calbec" is used. For calculations
in large unit cells, O(1000) atoms or so, distributing
such arrays (after reducing them to the strict minimum)
is often needed, but it seems to me that using band
distribution slows down things. An alternative solution
is to split the sum over beta functions.

P.
-- 
 Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
 Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
 Phone +39-0432-558216, fax +39-0432-558222