[gpaw-users] parallel settings

[Zhiyao Duan]

Thank you Ask.
I want to eventually calculate dielectric function of the system. From what I read from the online doc, pw mode isthe only mode that enable calculating dielectric function for an extended system, is that right?
Zhiyao

> Date: Thu, 12 Mar 2015 19:13:19 +0100
> Subject: Re: [gpaw-users] parallel settings
> From: asklarsen at gmail.com
> To: gump_813 at hotmail.com
> CC: gpaw-users at listserv.fysik.dtu.dk
> 
> Hello Zhiyao
> 
> You have 4 k-points which probably reduce to 2 in the irreducible BZ.
> 
> That means you have 48 cores sharing two k-points, so each group of 24
> will band parallelize amongst themselves as chosen by the defaults.
> Since PW mode does not have domain decompositions, the only allowed
> amount of band parallelization is 24 (wherefore 4 is an illegal
> number).  That's quite a lot and I would expect it to run a bit
> slowly.
> 
> As Marcin says, FD mode might well be more efficient.
> 
> Best regards
> Ask
> 
> 2015-03-12 17:22 GMT+01:00 Zhiyao Duan <gump_813 at hotmail.com>:
> > Hello everyone,
> >
> > I  am just starting to use gpaw and have a problem in setting parallel
> > parameters.
> > my system contains 96 atoms 840 valence electrons and 720 orbitals, 2 kpts
> > in IBZ and
> > grid points is  28*180*336. I was trying to
> > run the calculation with 48 cores using the following script:
> >
> > import numpy as np
> > from ase import Atoms
> > from gpaw import GPAW, PW, FermiDirac, MethfesselPaxton
> > from ase.optimize import FIRE,BFGS
> >
> > np.seterr(under="ignore")
> >
> > model=read('au_tio2.vasp',format='vasp')
> >
> > calc = GPAW(xc='PBE',
> >             mode='pw',
> >             kpts=(4, 1, 1),
> >             random=True,
> >             eigensolver='rmm-diis',
> >             txt='au_tio2_relax.txt')
> >
> > model.set_calculator(calc)
> > opt = BFGS(model)
> > opt.run(0.05)
> >
> > write('final_relax.vasp',model, format='vasp',direct=True)
> >
> > the job can run normally but much slower than vasp with similar setups.
> > I thought the slowness is due to parallelization, so I add
> > parallel={'band':4} to divide bands to 4 groups. This time the job failed
> > with
> > error:
> >
> > File "/usr/local/gpaw/lib/python/gpaw/mpi/__init__.py", line 939, in
> > autofinalize
> >     raise RuntimeError('All the CPUs must be used')
> > RuntimeError: All the CPUs must be used
> >
> > can anybody help me figuring out why this happens?
> >
> > Another question is how to compare the speed of gpaw and vasp?
> > As I mentioned above, on my system vasp seems much faster, maybe this is due
> > to number of valence electrons included in the calculation? In my case, Ti
> > atom has 12 valence electrons in gpaw comparing to 4 in vasp. Or the better
> > performance of vasp is
> > due to some other factors like parallelization?
> >
> > Thank you guys!
> >
> > Zhiyao
> >
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> > gpaw-users at listserv.fysik.dtu.dk
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