[Pw_forum] Memory issue in calculation with large unit-cell

[Paolo Giannozzi]

Knowing how much memory exactly a code uses is close to impossible. There
are some explanations about memory usage in the documentation:
http://www.quantum-espresso.org/wp-content/uploads/Doc/pw_user_guide/node13.html
The code prints out a list of the presumably largest arrays (it also prints
out, for some machines and compilers, the amount of dynamically allocated
arrays, not sure how reliable). This gives you at least a lower limit on
how much memory is needed (per process: on a multi-core machine, multiply
by the number of cores to have the total RAM). Note that using "Gamma
tricks" reduces a lot the amount of needed memory

Paolo


On Thu, Apr 14, 2016 at 10:03 AM, Elad Segev <eladsege at post.bgu.ac.il>
wrote:

> Dear QE users and developers,
>
> I running a pw 'relax' calculation in a unit cell with 512 atoms of GeSe
> with fcc symmetry and am running on a machine with 64 cores and 512GB RAM.
> I encountered difficulties when tried to run on all cores (64) and the
> memory usage was at 100% and started using the swap file heaviliy whille
> most of the cores are not running with full CPU but only ~1% .
>
> After trying to run on less cores on the macine, I ran on 16 cores and
> found that the memory usage was at 502GB and with no use of the swap file,
> all the cores are running at 100% CPU.
>
> I'm runinng this job with 1 k-point so npool=1.
> the MPI command is:
> mpirun pw.x -np 16 -npool 1 -nband 1 -ntg 1
> opmthreads=1
>
> Is there a solution in which I can run on all cores?
>
> Thanks in advance,
>
> Elad Segev,
> Ph.D. candidate
> Ilse KAtz Institute of Nanoscale science and technology
> Ben-Gurion University of the Negev, Israel
>
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>



-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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