Dear all,
I'm doing some test runs on bulk silicon, using QE 4.0.5. I need to calculate
the eigenvalues on dense k-points grids,
to test convergence of some properties. So, I did a simple scf + nscf runs with
with increasing (automatic) k-point grid
(from 8 8 8 1 1 1 to 24 24 24 1 1 1). The calculation is parallel and
uses 8 CPUs.
All the grids with a number of k-points > 804 show a strange behaviour, namely,
that once reached the 804th k-point
(so I see in the output the "Computing kpt #: 804" line) the calculation
remains running but no update of output files is done.
Has anybody experienced such kind of problem?
Just to help (me and you) to understand what is going on, I did some debug:
i) the problem disappears if I use -ndiag 1
(consider that if not specified, by default the parallel algorithm is used, the
output header contains
Iterative solution of the eigenvalue problem
a parallel distributed memory algorithm will be used,
eigenstates matrixes will be distributed block like on
ortho sub-group = 2* 2 procs
)
Of course, I don't know if in this case (that is, with -ndiag 1) the problem
could appear with much denser grids (e.g. 64 64 64 1 1 1), but
I would say not
ii) the problem is maybe a memory (allocation/deallocation?????) issue because
(see also point iv), if the parallel algorithm is used (which is what the code
chooses by default), the problem also disappears on decreasing the cutoff from
30 Ry to 15 Ry
iii) the code stops (in the sense that keeps running without doing anything) in
SUBROUTINE pcegterg (PW/cegterg.f90)
at the point
CALL zsqmred( nbase, vl, desc_old( nlax_ ), desc_old, nbase+notcnv, hl, nx,
desc )
(this means that the calculation of the 804th k-point executes the line
immediately before, but not the one immediately after)
Of course, all this provided I did my debug correctly.
iv) using QE 4.1.2 the code runs 25% slower and stops exactly at the same
k-point but in this case it doesn't keep running
(the code stops with a segmentation fault error)
Another issue I would like to point out is that, in the cases when the
calculation finishes correctly, the one with "-ndiag 1" runs much
faster (not sure but maybe half the time), so it could be better to set the
code in such a way that, in these "not-expensive" cases the
parallel diagonalization is disabled by default.
Giovanni
PS these are my input files:
>>>>>>>>>>>>>>>> Si.scf.in
&CONTROL
calculation = 'scf'
title = 'Si'
restart_mode = 'from_scratch'
outdir = '/scratch/cantele/prova'
prefix = 'Si'
pseudo_dir = '/home/nm_settings/software/CODES/Quantum-ESPRESSO/pseudo'
wf_collect = .true.
verbosity = 'high'
/
&SYSTEM
ibrav = 2
celldm(1) = 10.20927
nat = 2
ntyp = 1
ecutwfc = 30.0
/
&ELECTRONS
conv_thr = 1.0d-8
mixing_beta = 0.7
/
ATOMIC_SPECIES
Si 28.0855 Si.pz-vbc.UPF
ATOMIC_POSITIONS { alat }
Si 0.00 0.00 0.00
Si 0.25 0.25 0.25
K_POINTS { automatic }
8 8 8 0 0 0
>>>>>>>>>>>>>>>> Si.nscf.in
&CONTROL
calculation = 'nscf'
title = 'Si'
restart_mode = 'from_scratch'
outdir = '/scratch/cantele/prova'
prefix = 'Si'
pseudo_dir = '/home/nm_settings/software/CODES/Quantum-ESPRESSO/pseudo'
wf_collect = .true.
verbosity = 'high'
/
&SYSTEM
ibrav = 2
celldm(1) = 10.20927
nat = 2
ntyp = 1
ecutwfc = 30.0
nbnd = 60
/
&ELECTRONS
diago_full_acc = .true.
diago_thr_init = 1.0d-6
/
ATOMIC_SPECIES
Si 28.0855 Si.pz-vbc.UPF
ATOMIC_POSITIONS { alat }
Si 0.00 0.00 0.00
Si 0.25 0.25 0.25
K_POINTS { automatic }
24 24 24 1 1 1
--
Dr. Giovanni Cantele
Coherentia CNR-INFM and Dipartimento di Scienze Fisiche
Universita' di Napoli "Federico II"
Complesso Universitario di Monte S. Angelo - Ed. 6
Via Cintia, I-80126, Napoli, Italy
Phone: +39 081 676910
Fax: +39 081 676346
E-mail: giovanni.cantele at cnr.it
giovanni.cantele at na.infn.it
Web: http://people.na.infn.it/~cantele
Research Group: http://www.nanomat.unina.it
Skype contact: giocan74
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