text: Hi,I started the same input file doing a geometry optimization twice. One of the two geometry optimizations completed in 28 cycles the other failed after 50 cycles. Is this expected? I could imagine that there is some randomness in the initialization of the hessian matrix, is there a better way?
  Below is the input file.Thanks!Alberto
  optMethod = 'hf'
  optBasis = '6-311g*'
  finalMethod = 'mp2'
  finalBasis = 'aug-cc-pv[dt]z'
  import time
  t1 = time.time()
  def saveFile(name, string):
  f=open(name,'w')
  f.write(string)
  f.close()
  molecule rec0000004 {
  0 1
  C 19.421000 44.630001 30.513000
  C 20.502001 45.252998 29.702999
  C 20.663000 43.862999 30.209999
  C 20.482000 42.773998 29.070999
  O 19.398001 42.680000 28.385000
  N 21.586000 41.832001 28.763000
  C 21.386000 40.847000 27.728001
  C 21.709999 39.511002 28.292000
  C 22.889999 41.744999 29.422001
  C 23.785999 40.590000 29.018999
  N 23.125000 39.403999 28.490000
  C 23.771999 38.130001 28.141001
  O 23.066000 37.231998 27.705999
  C 25.247999 37.744999 28.232000
  C 25.604000 36.754002 29.219000
  C 26.160000 38.056000 27.202999
  F 25.826000 38.933998 26.233000
  C 27.476999 37.537998 27.212999
  C 27.827999 36.626999 28.232000
  C 26.872999 36.250999 29.233000
  C 27.319000 35.233002 30.304001
  C 26.165001 34.379002 30.886000
  C 25.993999 32.953999 30.659000
  C 26.878000 32.198002 29.760000
  C 26.622999 30.834999 29.514999
  C 25.556999 30.184000 30.177000
  C 24.684000 30.896999 31.062000
  C 24.934000 32.291000 31.320000
  C 24.100000 33.037998 32.240002
  O 23.179001 32.527000 32.881001
  N 24.285999 34.365002 32.410000
  N 25.365000 34.993999 31.766001
  H 19.228201 44.982498 31.537001
  H 18.470200 44.347698 30.037300
  H 20.350000 45.431900 28.628300
  H 21.107901 46.066700 30.128099
  H 21.385500 43.652599 31.012400
  H 20.338499 40.866001 27.392900
  H 22.047501 41.062199 26.875900
  H 21.194799 39.385601 29.255800
  H 21.377701 38.728401 27.594000
  H 23.433201 42.677299 29.208401
  H 22.710800 41.664700 30.504299
  H 24.478100 40.958302 28.247400
  H 24.357100 40.284901 29.908300
  H 24.874201 36.414001 29.938900
  H 28.194201 37.832001 26.460899
  H 28.823799 36.209801 28.257999
  H 28.055599 34.554100 29.849501
  H 27.790400 35.785400 31.130301
  H 27.719000 32.685699 29.289700
  H 27.242300 30.286501 28.820801
  H 25.397400 29.128599 30.012600
  H 23.849600 30.395100 31.529200
  H 23.663401 34.893398 32.987202
  no_com
  no_reorient
  }
  memory 8 Gb
  set basis $optBasis
  set opt_coordinates cartesian
  set optking dynamic_level 1
  optE, optWfn = optimize(optMethod, return_wfn=True)
  t2 = time.time()
  set basis $finalBasis
  I also see that the compute time can vary by as much as 25% even when the number of geometry optimization cycles is the same.
  I haven't tried out your input file or anything, but is there an intco.dat file left btwn optimizations? Or are you running both opt simultaneously out of the same dir? Those intco's can be insidious.
  intco.dat
  The two runs where started indifferent directories and I also created a separate scratch directory for each run and set the PSI_SCRATCH correspondingly.There were multiple jobs running in the same directory in one case but with different input file name and i see multiple intco files based on the input file name e.g.:
  singlePsi4_rec0000001.rec0000001.intcosinglePsi4_rec0000002.rec0000002.intco
  Thanks for looking into this!Alberto
  Is there a way to upload the output files?
  I think there's an upload button here on the forum. Otherwise a gist would do.
  Thanks,I uploaded the input and output files (two output files) to:
  Thanks for looking at this!Alberto
  Do the two optimizations take an identical first step or distinct ones?
  Besides the .intco file, there is the .1 binary file, but I doubt these are a problem if you are running in different directories.
  The input geometry of the second step is nearly identical between the two runs. Small changes do appear e.g.: C 19.648780860**9** 44.5171687685 29.9029085005vs. C 19.648780860**8** 44.5171687685 29.9029085004
  Thanks for taking a look!Alberto
  I reran the same input file twice on the same machine and noticed that even then there are slight differences even in the very first step of the SCF procedure.
  I ran using “set print 5” and looked for the first place where differences appear and it turns out to be in the “## C (Symmetry 0) ##” matrix following the “## F (Symmetry 0) ##” matrix.
  Below is the list of matrices the printed with the “set print 5” option. Op to the one highlighted all values are exactly identical between run one and run two. however after the highlighted one small differences are prevalent.
  The differences are small (-0.10116103981167 vs 0.10116103981170) but i do not understand why the calculation is not exactly reproducible on the same machine and the differences could add up. Could there be a variable that is not initialized?
  Thanks,
  Alberto
  ## One-electron Hamiltonian (Symmetry 0) ##
  ## S (Symmetry 0) ##
  ## X (Symmetry 0) ##
  ## C (Symmetry 0) ##
  ## C (Symmetry 0) ##
  ## SCF density (Symmetry 0) ##
  ## SCF density (Symmetry 0) ##
  ## F (Symmetry 0) ##
  ## F (Symmetry 0) ##
  ## F (Symmetry 0) ##
  ## F (Symmetry 0) ##
  ## C (Symmetry 0) ## <------------------------------- Differences start here
  The value difference is around machine epsilon, and computers are not completely deterministic these days with respect to these tiny differences. This is especially true considering that the diagonalizer is iterative and QM computations are fairly sensitive in nature.