[CPMD-list] increased CPU times for wavefunction iterations

[Martin Konopka]

Dear CPMD developers,

May I have few questions on wavefunction optimization, in particular CPU
times for individual iterations? The usual pattern is that first part of
them takes one value of CPU time (about 82 s in the example below) but the
other part spends significantly more time (here 121 s). I see that this
larger value occurs when wavefunctions are almost converged; often it is
only in last one or two iterations but sometime in more of them.

I can notice this behaviour at least when using Vanderbilt
pseudopotentials.

What is a more detailed reason for this?

Is it possible to avoid the incresed CPU times somehow (except cutting
down the number of iterations)?


RESETTING WAVEFUNCTION TOLERANCE FACTOR TO:  1.0
   1  1.274E-05   2.093E-06   -2003.766203    6.517E-06     82.41
   2  1.418E-05   7.662E-07   -2003.766206   -3.192E-06     81.77
   3  1.423E-05   6.226E-07   -2003.766206   -3.597E-07     81.00
   4  1.120E-05   3.037E-07   -2003.766207   -3.911E-07     82.17
   5  9.869E-06   2.593E-07   -2003.766207   -1.469E-07     81.38
   6  9.743E-06   2.190E-07   -2003.766207   -2.256E-07     81.62
   7  8.522E-06   1.914E-07   -2003.766208   -3.139E-07     81.72
   8  7.540E-06   1.659E-07   -2003.766208   -2.474E-07     83.64
   9  6.717E-06   1.455E-07   -2003.766208   -1.815E-07     82.54
  10  5.885E-06   1.346E-07   -2003.766208   -1.956E-07     82.62
 RELAXING WAVEFUNCTION TOLERANCE, NEW FACTOR:  2.0
  11  5.428E-06   1.274E-07   -2003.766208   -1.691E-07     82.66
  12  4.997E-06   1.185E-07   -2003.766208   -1.303E-07    121.48
  13  4.565E-06   1.093E-07   -2003.766209   -1.725E-07    121.36
  14  4.126E-06   9.982E-08   -2003.766209   -1.418E-07    120.97
  15  3.850E-06   8.996E-08   -2003.766209   -1.009E-07    120.63
  16  3.854E-06   8.264E-08   -2003.766209   -1.117E-07    120.15
  17  3.879E-06   7.954E-08   -2003.766209   -9.304E-08    121.96
  18  3.662E-06   7.727E-08   -2003.766209   -7.082E-08    121.41
  19  3.680E-06   7.516E-08   -2003.766209   -8.924E-08    119.64
  20  3.410E-06   7.326E-08   -2003.766209   -8.909E-08    120.40

Thanks for your help.
Martin Konopka.



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Dr. Martin Konopka             http://www.ccms.elf.stuba.sk/konopka.html
Department of Physics, CCMS                      tel: +421 (0)2 60291714
Slovak University of Technology (FEI STU)        fax: +421 (0)2 65411483
Ilkovicova 3, 812 19 Bratislava, Slovakia
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