[Pw_forum] about OMP_NUM_THREADS

Jason Larkin jmlarkin at andrew.cmu.edu
Fri Sep 25 16:06:16 CEST 2009


Hello Forum,

First, thanks very much for the great software package. Here is my 
issue, one which is probably due to my own ignorance about QE/quantum 
physics in general:

I'm trying to run a varaible cell relaxation on the compound GeTe.  
Below is my input file:

 &control
    calculation = 'vc-relax'
    prefix='gt',
    pseudo_dir = '$HOME/pseudo/',
    outdir='$HOME/QE/GST/GeTe/out/'
    forc_conv_thr = 1.0d-5,
    etot_conv_thr = 1.0d-5,
    nstep=300,
/
 &system   
    ibrav = 4, celldm(1)=7.993540933, celldm(3)=2.581560284
    nat = 18, ntyp= 2,
    ecutwfc = 100, ecutrho = 800,
 /
 &electrons
    mixing_beta = 0.7
    conv_thr = 1.0d-6,
 /
 &ions
  upscale = 100.d0,
 /
 &cell
    cell_dynamics='damp-w'
 /
ATOMIC_SPECIES
 Te  1.0 Te.pz-bhs.UPF
 Ge  1.0 Ge.pz-bhs.UPF
ATOMIC_POSITIONS {crystal}
Te    0    0    0
Ge    0.666666    0.333333    0.055555556
Te    0.33333    0.666666    0.111111111
Ge    0    0    0.166666667
Te    0.6666666    0.3333333    0.222222222
Ge    0.3333333    0.6666666    0.277777778
Te    0    0    0.333333333
Ge    0.6666666    0.3333333    0.388888889
Te    0.3333333    0.6666666    0.444444444
Ge    0    0    0.5
Te    0.6666666    0.3333333    0.555555556
Ge    0.3333333    0.6666666    0.611111111
Te    0    0    0.666666667
Ge    0.6666666    0.3333333    0.722222222
Te    0.3333333    0.6666666    0.777777778
Ge    0    0    0.833333333
Te    0.6666666    0.3333333    0.888888889
Ge    0.3333333    0.6666666    0.944444444
K_POINTS {automatic}
 12 12 2 0 0 0 

My problem (issue) is this; the simulation continues to time out before 
completing the relaxation.  As such, I've been coninuously increasing 
the amount of time and processors that I am requesting to perform this 
calculation.  However, it has reached a point (32 processors and 3:30 
hours) where I'm almost certain that I am doing something wrong.  I was 
able to find one forum posting where a user was running a relaxation and 
the calculation was not stopping even though the Energy and Force 
calculation error thresh holds where being satisfied. It appears that my 
energy does indeed converge.   Let me attach part of my output:

*********************************************************************
!    total energy              =  -203.60367909 Ry
     Harris-Foulkes estimate   =  -203.60367961 Ry
     estimated scf accuracy    <     0.00000054 Ry

     convergence has been achieved in   9 iterations

     Forces acting on atoms (Ry/au):

     atom   1 type  1   force =     0.00000000    0.00000000    0.00000000
     atom   2 type  2   force =     0.00000000    0.00000000    0.00052582
     atom   3 type  1   force =     0.00000000    0.00000000   -0.00108418
     atom   4 type  2   force =     0.00000000    0.00000000   -0.00111021
     atom   5 type  1   force =     0.00000000    0.00000000   -0.00066898
     atom   6 type  2   force =     0.00000000    0.00000000    0.00030722
     atom   7 type  1   force =     0.00000000    0.00000000   -0.00150570
     atom   8 type  2   force =     0.00000000    0.00000000   -0.00163780
     atom   9 type  1   force =     0.00000000    0.00000000    0.00177984
     atom  10 type  2   force =     0.00000000    0.00000000    0.00000000
     atom  11 type  1   force =     0.00000000    0.00000000   -0.00177984
     atom  12 type  2   force =     0.00000000    0.00000000    0.00163780
     atom  13 type  1   force =     0.00000000    0.00000000    0.00150570
     atom  14 type  2   force =     0.00000000    0.00000000   -0.00030722
     atom  15 type  1   force =     0.00000000    0.00000000    0.00066898
     atom  16 type  2   force =     0.00000000    0.00000000    0.00111021
     atom  17 type  1   force =     0.00000000    0.00000000    0.00108418
     atom  18 type  2   force =     0.00000000    0.00000000   -0.00052582

     Total force =     0.004763     Total SCF correction =     0.002516


     entering subroutine stress ...

          total   stress  (Ry/bohr**3)                   (kbar)     P= 
5650.32
   0.02322957   0.00000000   0.00000000       3417.19      0.00      0.00
   0.00000000   0.02322957   0.00000000          0.00   3417.19      0.00
   0.00000000   0.00000000   0.06877108          0.00      0.00  10116.57


     Wentzcovitch Damped Cell-Dynamics Minimization
     convergence thresholds: EPSE = 0.10E-04  EPSF = 0.10E-04  EPSP = 
0.50E+00

     Entering Dynamics;  it =     1   time =  0.00000 pico-seconds
*********************************************************************



The simulation goes through 23 complete Self-consistent Calculations. 
Here is the last self-consistent run (before the 24th run timed out):



*********************************************************************
!    total energy              =  -216.83428802 Ry
     Harris-Foulkes estimate   =  -216.83428838 Ry
     estimated scf accuracy    <     0.00000036 Ry

     convergence has been achieved in  10 iterations

     Forces acting on atoms (Ry/au):

     atom   1 type  1   force =     0.00000000    0.00000000    0.00000000
     atom   2 type  2   force =     0.00000000    0.00000000   -0.00120296
     atom   3 type  1   force =     0.00000000    0.00000000   -0.00028879
     atom   4 type  2   force =     0.00000000    0.00000000    0.00057200
     atom   5 type  1   force =     0.00000000    0.00000000    0.00115400
     atom   6 type  2   force =     0.00000000    0.00000000   -0.00030438
     atom   7 type  1   force =     0.00000000    0.00000000   -0.00064802
     atom   8 type  2   force =     0.00000000    0.00000000   -0.00012442
     atom   9 type  1   force =     0.00000000    0.00000000    0.00095840
     atom  10 type  2   force =     0.00000000    0.00000000    0.00000000
     atom  11 type  1   force =     0.00000000    0.00000000   -0.00095840
     atom  12 type  2   force =     0.00000000    0.00000000    0.00012442
     atom  13 type  1   force =     0.00000000    0.00000000    0.00064802
     atom  14 type  2   force =     0.00000000    0.00000000    0.00030438
     atom  15 type  1   force =     0.00000000    0.00000000   -0.00115400
     atom  16 type  2   force =     0.00000000    0.00000000   -0.00057200
     atom  17 type  1   force =     0.00000000    0.00000000    0.00028879
     atom  18 type  2   force =     0.00000000    0.00000000    0.00120296

     Total force =     0.003045     Total SCF correction =     0.001829


     entering subroutine stress ...

          total   stress  (Ry/bohr**3)                   (kbar)     P= 
1021.47
   0.00437252   0.00000000   0.00000000        643.22      0.00      0.00
   0.00000000   0.00437252   0.00000000          0.00    643.22      0.00
   0.00000000   0.00000000   0.01208629          0.00      0.00   1777.95


     Entering Dynamics;  it =    24   time =  0.02226 pico-seconds
*********************************************************************



It appears that my force(s) are not consistent with the force threshold 
that I set. I'm guessing this is because my initial guess at the 
structure is quite far from the relaxed structure.  So, would it be 
reasonable to take the unit cell coordinates from the last completed 
self-consistent calcualtion and use those as starting coordinates for a 
brand new vc-relax run? This would be an effort to continue the 
calculation, but not lose the 3:30 of run time I've already used.  Also, 
how would I handle a restart in this situation? Forgive me if this 
question is too basic.  Thanks for the help





Jason Larkin, PhD Student
Carnegie Mellon University




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