[Pw_forum] setting grid size and memory management for pw scf

Lorenzo Paulatto lorenzo.paulatto at impmc.upmc.fr
Sat Jan 12 14:49:22 CET 2013

On 11 January 2013 17:06, Mike Marchywka <marchywka at hotmail.com> wrote:

> I'm try do dft on about 24 atoms using laptop and the thing runs out of
> real memory.
> I set diagnolaization to cg which may have solved the immediate problem
> but curious
> on what other things I can do.
> Thanks.

You should not change the size of the fft grid by hand, except in some very
specific case. What you change are the wavefunctions and charge density
cutoffs, which are system independent and have some sort of physical
meaning. These cutoffs in turn control the fft grid.

Of course you cannot just reduce the cutoff, you need to test convergence
and use a converged value. If you are running out of memory you can either
but a bigger computer or study a smaller system. In some specific case
changing the parallelism scheme or some computation parameter can help.


Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
phone: +33 (0)1 44275 084 / skype: paulatz
www:   http://www-int.impmc.upmc.fr/~paulatto/
mail:  23-24/4é16 Boîte courrier 115, 4 place Jussieu 75252 Paris Cédex 05
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