[Pw_forum] parallel efficiency for large system

[Yuyang Zhang]

Dear All,

I am now carrying on the calculation for a system with 2300 electrons in a
20x22x25 angstrom^3 supercell.

I always submit jobs on a blue-gene type machine with 512 CPUs (power 470)
connected with infiniband.

In VASP, time scale for a single SCF step is about 150 sec (spin polarized,
gamma point only, 400 eV energy cutoff)

In PWSCF, with a 25Ry energy cutoff, a single SCF step will take 3000 sec
(spin polarized , gamma point only, -npool=2).

I check "massive parallel" on the manual and the arxive of this mailing
list, and try to use -ntg tag when submitting the jobs but no significant
improvement.

There is no reason that PWSCF runs 20 times slower than VASP.  Does anyone
have experience to improve the parallel efficiency for these large systems?

Best,

Yuyang Zhang

Nanoscale Physics and Devices Laboratory
Institute of Physics, Chinese Academy of Sciences
Beijing 100190, P. R. China
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