[QE-users] Huge memory requirements for a scf calculation of a system consisting with 300+ atoms.

[Sebastian Hütter]

Hi,

This may be a stupid question, but...

>       Estimated static dynamical RAM per process >       3.32 GB
>       Estimated max dynamical RAM per process >      10.52 GB
>       Estimated total dynamical RAM >     462.96 GB

... is this not expected behavior? I'm not super experienced, so I just assumed it was.

Your numbers pretty much match what I see in terms of "RAM per Cell volume" in metals with non-symmetric unit cells 
using PAW pseudos, if not less. Random example: 126 atoms, 63 k-points, ~1000 bands, 250³ dense grid FFT gives ~10GB per 
rank, for a total of 680GB with 64 ranks. I actually plan node requests for our cluster based entirely on memory 
required, probably wasting CPU time along the way (4N*16C in the example above).

Reasonable ke and charge cutoffs seem to blow up the memory requirements a lot. Of course multiplied by the number of 
bands...


Best,

Sebastian


--
M.Sc. Sebastian Hütter
Otto-von-Guericke University Magdeburg
Institute of Materials and Joining Technology