[QE-users] pp.x calculation very slow

Wed Mar 24 14:57:59 CET 2021

Dear Professor Giannozzi,

I understand. Then this half an hour is consistent with my calculations and
I will simply have to deal with the computation time
Thanks again!

Kind regards
Lenz

Am Mi., 24. März 2021 um 14:51 Uhr schrieb Paolo Giannozzi <
p.giannozzi at gmail.com>:

> On Tue, Mar 23, 2021 at 10:28 PM Lenz Fiedler <fiedler.lenz at gmail.com>
> wrote:
>
> So if I understand you correctly, you did something like
>>    mpirun -np 18 pp.x -in Fe.pp.ldos.in
>> on the nscf data wirh 14x14x14 and got the 560 cube files in 30 minutes?
>>
>
> I computed only ONE cube file, I don't remember for which k-point grid.
> You may want to make a few tests with a smaller k-point grid and for a
> single energy. Then you can easily guess what will be the needed time for
> your complete case. Anyway: if you need so many energies with a dense
> k-point grid, it will take a lot of time no matter what.
>
> Paolo
>
> This is what I would expect/hope for as well. I will try this and if I
>> cannot reproduce it there might be something wrong with my installation.
>>
>> Kind regards
>> Lenz
>>
>>
>> Am So., 21. März 2021 um 16:31 Uhr schrieb Paolo Giannozzi <
>> p.giannozzi at gmail.com>:
>>
>>> A LDOS calculation should take more or less the same time as the
>>> calculation of the charge density, plus reading, wroting, etc.. I just
>>> tried and it took half an hour on 18 processors (CPU cores, not GPUs)
>>>
>>> Paolo
>>>
>>> On Wed, Mar 17, 2021 at 5:26 PM Lenz Fiedler <fiedler.lenz at gmail.com>
>>> wrote:
>>>
>>>> Dear Professor Giannozzi,
>>>>
>>>> Thank you so much for your answer. You are right, I did not really
>>>> think about the parallelization for the initial SCF calculation, I was more
>>>> puzzled by the pp.x calculation. If I understand you correctly, using
>>>> something like "pp.x -nk 16" might also help speed up the LDOS calculation
>>>> as well? But there also might be an upper limit of how fast this performs
>>>> and it could be that I simply have to wait a while to obtain the LDOS? As
>>>> in, except for my suboptimal parallelization strategy, the long runtime of
>>>> pp.x I observed was not due to wrong usage but simply to computational load
>>>> of the problem?
>>>>
>>>> Kind regards
>>>> Lenz Fiedler
>>>>
>>>> PhD Student (HZDR / CASUS)
>>>>
>>>>
>>>> Am Di., 16. März 2021 um 16:36 Uhr schrieb Paolo Giannozzi <
>>>> p.giannozzi at gmail.com>:
>>>>
>>>>> Your supercell is small but you have a high cutoff and a large number
>>>>> of k-points, which makes the overall computational load quite heavy.
>>>>> Moreover your choice of parallelization is less than optimal: you should
>>>>> use both k-point and plane-wave parallelization, something like "mpirun -np
>>>>> 160 pw.x -nk 16" or so. For reference: I ran your Fe.pw.scf.in input
>>>>> in 20' on a small 36-core machine with two (powerful) GPU's. The nscf
>>>>> calculation took 1h20' for the calculation and is taking as much time if
>>>>> not more to write the files. Also note that not all postprocessing
>>>>> calculations are optimized for large runs.
>>>>>
>>>>> Paolo
>>>>>
>>>>> On Mon, Mar 15, 2021 at 7:23 PM Lenz Fiedler <fiedler.lenz at gmail.com>
>>>>> wrote:
>>>>>
>>>>>> (resent because something went wrong with the header line)
>>>>>>
>>>>>> Hi users,
>>>>>>
>>>>>> I am experiencing a problem with pp.x. I want to calculate the LDOS
>>>>>> for a 16 Fe atom supercell using a 560 value energy grid and the 3D grid
>>>>>> given by the DFT calculation (100x100x100 grid points). I have performed
>>>>>> the DFT calculation by first doing a SCF calculation (8x8x8 k-points) and
>>>>>> then a non-SCF calculation (14x14x14 k-points) successfully. Now I am
>>>>>> trying to do:
>>>>>>
>>>>>> mpirun -np 160 pp.x -in Fe.pp.ldos.in
>>>>>>
>>>>>> but the calculation takes way longer than I anticipated. The entire
>>>>>> DFT calculation took less than a day, while for the LDOS, after about 12
>>>>>> hours, only 20 tmp files had been written. Am I doing something wrong? Or
>>>>>> is this expected? At this rate, calculating the LDOS would take days, which
>>>>>> is why I am assuming I am doing something wrong.
>>>>>> Please find my output and input files here:
>>>>>>
>>>>>>
>>>>>> https://drive.google.com/drive/folders/1R-m5jlw1bcNxe3nBXjc4dms-IoMMp4Ir?usp=sharing
>>>>>> (the pp.out file is from a run where I investigated if a lower number
>>>>>> of CPUs helps, but that was slower, as expected.)
>>>>>>
>>>>>> Kind regards
>>>>>> Lenz
>>>>>>
>>>>>> PhD Student (HZDR / CASUS)
>>>>>> _______________________________________________
>>>>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>>>>>> users mailing list users at lists.quantum-espresso.org
>>>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>>>>> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
>>>>> Phone +39-0432-558216, fax +39-0432-558222
>>>>>
>>>>> _______________________________________________
>>>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>>>>> users mailing list users at lists.quantum-espresso.org
>>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>>
>>>> _______________________________________________
>>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>>>> users mailing list users at lists.quantum-espresso.org
>>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>>
>>>
>>>
>>> --
>>> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
>>> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
>>> Phone +39-0432-558216, fax +39-0432-558222
>>>
>>> _______________________________________________
>>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>> _______________________________________________
>> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
>> users mailing list users at lists.quantum-espresso.org
>> https://lists.quantum-espresso.org/mailman/listinfo/users
>
>
>
> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 206, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
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