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.
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.
you can use wf_collect=.true. and increase the number of processors.
stefano
On 05/12/2015 12:57, Maxim Skripnik wrote:
Thank you for the information. Yes, at the beginning of the pw.x
output it says:
Parallel version (MPI), running on 64 processors
R & G space division: proc/nbgrp/npool/nimage = 64
Is bands.x parallelized at all? If so, where can I find information on
that? There's nothing mentioned in the documentation:
http://www.quantum-espresso.org/wp-content/uploads/Doc/pp_user_guide.pdf
http://www.quantum-espresso.org/wp-content/uploads/Doc/INPUT_BANDS.html
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:
&bands
prefix = 'st1'
outdir = './tmp'
/
The calculation is initiated by
mpirun -np 64 bands.x < job.bands
Maxim Skripnik
Department of Physics
University of Konstanz
Am Samstag, 05. Dezember 2015 02:37 CET, stefano de gironcoli
<[email protected]> schrieb:
On 04/12/2015 22:53, Maxim Skripnik wrote:
Hello,
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
mpirun -np 128 pw.x < job.pw
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?
R and G parallelization is performed.
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.
Did you had a look to it ?
Second question is, whether one can speed up bands.x calculations. Up
to now I start these this way:
mpirun -np 64 bands.x < job.bands
on 4 nodes, 16 cores each. Does it make sense to define nb for
bands.x? If yes, what would be reasonable values?
expect no gain. band parallelization is not implemented in bands.
stefano
The systems of interest consist of typically ~50 atoms with periodic
boundaries.
Maxim Skripnik
Department of Physics
University of Konstanz
_______________________________________________
Pw_forum mailing list
[email protected]
http://pwscf.org/mailman/listinfo/pw_forum
_______________________________________________
Pw_forum mailing list
[email protected]
http://pwscf.org/mailman/listinfo/pw_forum
_______________________________________________
Pw_forum mailing list
[email protected]
http://pwscf.org/mailman/listinfo/pw_forum
