[Pw_forum] computation time of addusdens subroutine

[Junfeng Qiao]

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