[Q-e-developers] Plotting many KS orbitals in one pp.x run (and more)

[Paolo Giannozzi]

In my opinion, the postprocessing code "pp.x" is a mess beyond control that
badly needs to be split, re-organized and cleaned up. This being said: your
patch adds a negligible amount of entropy, so I do not personally see major
reasons not to accept it. I would however avoid changes to the symmetry
section: it is sufficient to call "sym_rho_init" just once, outside the
loop over k-points and bands. I would also avoid adding new "plot_num"
values since there are no new quantities to be plotted, just new options to
plot them

Paolo

On Mon, Nov 7, 2016 at 6:05 PM, Leopold Talirz <leopold.talirz at gmail.com>
wrote:

> Dear QE developers,
>
> this is a feature request, which I am sending to the mailing list in lieu
> of access to the QE bug tracker on qe-forge.org
>
>
> I am sure many of you are familiar with the AiiDA project (
> http://www.aiida.net/), which provides not only a very convenient python
> infrastructure for running QE calculations, but also a database for a
> consistent storage of results.
>
> We have recently come across a "conflict of philosophy" between QE (more
> specifically, pp.x) and AiiDA that causes considerable computational/data
> overhead.
>
> Basically, we need to plot lots of KS orbitals for different
> nanostructures.
> pp.x is designed to produce 1 cube file per execution and AiiDA is
> designed to produce 1 working directory per calculation.
> I.e. when computing 100 KS orbitals from a band structure calculation,
> using AiiDA the information contained in the band structure directory is
> replicated 100 times.
>
> Our solution so far has been to modify the source of pp.x in such a way
> that one run can produce N KS orbitals. This has the added benefit of
> saving a lot of "startup time" as compared to running pp.x N times (in a
> test run generating 21 KS orbitals, the speedup was ~3x but this does vary,
> of course).
> We have already contacted AiiDA developers Nicolas Mounet and Giovanni
> Pizzi and they are in favor of this solution as well.
>
> I attach a patch against QE 6.0 (git SHA 93ced686f67fe1f3250824358015e2ffde364960)
> that adds plot_num 22 and 23 in pp.x.
> plot_num 23 allows to plot N KS orbitals and plot_num 22 allows to plot
> the local density of states on a grid of energies between emin and emax
> (useful for scanning tunneling spectroscopy simulations). The patch starts
> with a commit message that contains sample input files.
>
> I think the main question is, whether you would consider deviating from
> the "1 run = 1 output file" policy.
> If yes, then one can think of the details regarding the implementation
> (the patch, including the input format for the KS orbitals, can certainly
> be improved).
>
> Best wishes,
> Leopold Talirz, Carlo Pignedoli and Sasha Yakutovich
>
>
>
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> Q-e-developers at qe-forge.org
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>
>


-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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