[QE-users] Optimal pw command line for large systems and only Gamma point

[Paolo Giannozzi]

On 5/10/24 08:58, Antonio Cammarata via users wrote:

> pw.x -nk 1 -nt 1 -nb 1 -nd 768 -inp qe.in > qe.out

too many processors for linear-algebra parallelization. 1000 Si atoms = 
2000 bands (assuming an insulator with no spin polarization). Use a few 
tens of processors at most

> "some processors have no G-vectors for symmetrization". 

which sounds strange to me: with the Gamma point symmetrization is not 
even needed


>       Dense  grid: 30754065 G-vectors     FFT dimensions: ( 400, 400, 400)

This is what a 256-atom Si supercell with 30 Ry cutoff yields:

      Dense  grid:   825897 G-vectors     FFT dimensions: ( 162, 162, 162)

I guess you may reduce the size of your supercell

Paolo

>       Dynamical RAM for                 wfc:     153.50 MB
>       Dynamical RAM for     wfc (w. buffer):     153.50 MB
>       Dynamical RAM for           str. fact:       0.61 MB
>       Dynamical RAM for           local pot:       0.00 MB
>       Dynamical RAM for          nlocal pot:    1374.66 MB
>       Dynamical RAM for                qrad:       0.87 MB
>       Dynamical RAM for          rho,v,vnew:       5.50 MB
>       Dynamical RAM for               rhoin:       1.83 MB
>       Dynamical RAM for            rho*nmix:       9.78 MB
>       Dynamical RAM for           G-vectors:       2.60 MB
>       Dynamical RAM for          h,s,v(r/c):       0.25 MB
>       Dynamical RAM for          <psi|beta>:     552.06 MB
>       Dynamical RAM for      wfcinit/wfcrot:     977.20 MB
>       Estimated static dynamical RAM per process >       1.51 GB
>       Estimated max dynamical RAM per process >       2.47 GB
>       Estimated total dynamical RAM >    1900.41 GB
> 
> I managed to run the simulation with 512 atoms, cg diagonalization and 3 
> nodes on the same machine with command line
> 
> pw.x -nk 1 -nt 1 -nd 484 -inp qe.in > qe.out
> 
> Please, do you have any suggestion on how to set optimal parallelization 
> parameters to avoid the memory issue and run the calculation? I am also 
> planning to run simulations on nanoclusters with more than 1000 atoms.
> 
> Thanks a lot in advance for your kind help.
> 
> Antonio
> 
> 

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