[Pw_forum] default parallelization and parallelization of bands.x

[Maxim Skripnik]

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?

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?

The systems of interest consist of typically ~50 atoms with periodic boundaries.

Maxim Skripnik
Department of Physics
University of Konstanz
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20151204/7a1165e8/attachment.html>