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<div class="moz-cite-prefix">The only parallelization that i see in
bands is the basic one over R & G. If it is different from the
parallelization used previously you should use wf_collect.<br>
the code computes the overlap between the orbital at k and k+dk in
order to decide how to connect them. it's an nbnd^2 operation done
band by band. not very efficient evidently but it should not take
hours.<br>
you can use wf_collect=.true. and increase the number of
processors.<br>
<br>
stefano<br>
<br>
<br>
On 05/12/2015 12:57, Maxim Skripnik wrote:<br>
</div>
<blockquote
cite="mid:53cdc7c4e767a41e.5662d119@limbe.rz.uni-konstanz.de"
type="cite">Thank you for the information. Yes, at the beginning
of the pw.x output it says:<br>
Parallel version (MPI), running on 64 processors<br>
R & G space division: proc/nbgrp/npool/nimage = 64<br>
<br>
Is bands.x parallelized at all? If so, where can I find
information on that? There's nothing mentioned in the
documentation:<br>
<a class="moz-txt-link-freetext" href="http://www.quantum-espresso.org/wp-content/uploads/Doc/pp_user_guide.pdf">http://www.quantum-espresso.org/wp-content/uploads/Doc/pp_user_guide.pdf</a><br>
<a class="moz-txt-link-freetext" href="http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_BANDS.html">http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_BANDS.html</a><br>
<br>
What could be the reason for bands.x taking many hours to
calculate the bands? The foregoing pw.x calculation has already
determined the energy for each k-point along a path (Gamma -> K
-> M -> Gamma). There are 61 k-points and 129 bands. So what
is bands.x actaully doing beside reformating that data? The input
file job.bands looks like this:<br>
&bands<br>
prefix = 'st1'<br>
outdir = './tmp'<br>
/<br>
The calculation is initiated by<br>
mpirun -np 64 bands.x < job.bands<br>
<br>
Maxim Skripnik<br>
Department of Physics<br>
University of Konstanz<br>
<br>
Am Samstag, 05. Dezember 2015 02:37 CET, stefano de gironcoli
<a class="moz-txt-link-rfc2396E" href="mailto:degironc@sissa.it"><degironc@sissa.it></a> schrieb:<br>
<blockquote type="cite" cite="56623FC2.9070705@sissa.it"> </blockquote>
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<div class="moz-cite-prefix">On 04/12/2015 22:53, Maxim Skripnik
wrote:</div>
<blockquote
cite="mid:bbc1c3d2d4083244.56620b59@limbe.rz.uni-konstanz.de"
type="cite">Hello,<br>
<br>
I'm a bit confused by the parallelization scheme of QE. First of
all, I run calculations on a cluster with usually 1 to 8 nodes,
each of which has 16 cores. There is a very good scaling of pw.x
e.g. for structural relaxation jobs. I do not specify any
particular parallelization scheme as mentioned in the
documentation, i.e. I start the calculations with<br>
mpirun -np 128 pw.x < job.pw<br>
on 8 nodes, 16 cores each. According to the documentation ni=1,
nk=1 and nt=1. So in which respect are the calculations
parallelized by default? Why do the calculations scale so well
without specifying ni, nk, nt, nd?</blockquote>
R and G parallelization is performed.<br>
wavefunctions' planewaves, density planewaves and slices of real
space objects are distributed across 128 processors. A report of
how this is done is given at the beginning of the output.<br>
Did you had a look to it ?<br>
<blockquote
cite="mid:bbc1c3d2d4083244.56620b59@limbe.rz.uni-konstanz.de"
type="cite">Second question is, whether one can speed up bands.x
calculations. Up to now I start these this way:<br>
mpirun -np 64 bands.x < job.bands<br>
on 4 nodes, 16 cores each. Does it make sense to define nb for
bands.x? If yes, what would be reasonable values?</blockquote>
expect no gain. band parallelization is not implemented in bands.<br>
<br>
stefano<br>
<br>
<br>
<br>
<br>
<br>
<br>
<blockquote
cite="mid:bbc1c3d2d4083244.56620b59@limbe.rz.uni-konstanz.de"
type="cite">The systems of interest consist of typically ~50
atoms with periodic boundaries.<br>
<br>
Maxim Skripnik<br>
Department of Physics<br>
University of Konstanz
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