[Pw_forum] computation time of addusdens subroutine

[stefano de gironcoli]

You can try to see if the postprocess code accepts the calculation of 
augmentation charge in real space (tqr=.true. in some namelist , I guess 
electrons)
If it works it should be faster
stefano

On 11/07/2017 16:04, Junfeng Qiao wrote:
> Dear QE users,
>
> I am currently trying to extract wavefunction |psi|^2 of some bands and
> kpoints, which can be achieved with plot_num = 7 of pp.x.
>
> However, if I extract large amount of wavefunctions, for example, assigning
> kpoint(1) = 1, kpoint(2) = 20*20, kband(1) = 1, kband(2) = 300,
> the pp.x will run for an unbearable long time.
>
> On my cluster (10 intel cpus, total 60 cores), each wavefunction will take
> about 8 seconds, and do a simple prediction, in total 8 * (20*20) * 300 / 3600
> / 24 = 11 days ! It is much more longer than the scf calculations.
>
> After playing with the code(QE v6.1), I found in local_dos.f90 line 392, the
> call to addusdens() takes up almost all the computation time, other parts are
> negligible.
>
> While, in this situation, I totally have no ideas how to get out of this
> trouble, so I am seeking for help in this community: is it possible to speed
> up this addusdens() part?
>
> Thanks for your time of reading this email, any suggestions will be truly
> appreciated.
>
> Sincerely,
> Junfeng Qiao
> Beihang University (BUAA)
> Beijing, China
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