[Pw_forum] huge memory usage in ibrav=1

[Carlo Nervi]

Dear QE community,
I recently tried to run a simple calculation using a large supercell 
with ibrav=1. The cell contains 13 atoms.
pw.x runs, but consumes a huge amount of memory (in the example below 
more than 400 Mb of ram for each pw.x process). If I set A = 50.0 it 
consumes more than 1Gb of RAM for each process, and of course having 8 
cPU and 8 Gb of RAM the calculation continously swap with the disk...
Perhaps I'm doing something wrong, but I cannot find the reason.

The data are derived from an analogue calculation where 104 atoms were 
present in the cell for a real periodic calculation. This optimization 
runs without any problem.

I'm using QE 4.1.2. I would appreciate any suggestion.
Thanks,
	Carlo

---------

  &CONTROL
                        title = 'Barb_gas2' ,
                  calculation = 'relax' ,
                 restart_mode = 'from_scratch' ,
                       outdir = './' ,
                   pseudo_dir = '../PP/' ,
                       prefix = 'Barb_gas2' ,
                      disk_io = 'default' ,
                    verbosity = 'default' ,
                etot_conv_thr = 1e-4 ,
                forc_conv_thr = 1e-3 ,
                        nstep = 256 ,
                       iprint = 1,
                      tstress = .true. ,
                      tprnfor = .true. ,
  /
  &SYSTEM
                        ibrav = 1,
                            A = 10.0 ,
                            B = 10.0 ,
                            C = 10.0 ,
                        cosAB = 0.0d0 ,
                        cosAC = 0.0 ,
                        cosBC = 0.0d0 ,
                          nat = 13,
                         ntyp = 4,
                      ecutwfc = 120 ,
                        nosym = .true. ,
  /
  &ELECTRONS
             electron_maxstep = 256,
                     conv_thr = 1.0D-6 ,
                  startingpot = 'atomic' ,
                  startingwfc = 'atomic' ,
                  mixing_mode = 'plain' ,
                  mixing_beta = 0.7D0 ,
                  mixing_ndim = 8,
              diagonalization = 'david' ,
  /
  &IONS
                 ion_dynamics = 'bfgs' ,
  /
ATOMIC_SPECIES
     H    1.00794  H.pbe-tm-gipaw.UPF
     O   15.99940  O.pbe-tm-gipaw.UPF
     C   12.01070  C.pbe-tm-gipaw.UPF
     N   14.00674  N.pbe-tm-gipaw.UPF
ATOMIC_POSITIONS (angstrom)
  O                  4.54996963    4.16012233    3.24841463
  O                  4.27040451    8.61116200    3.94060959
  O                  1.70010607    5.59594564    6.44124884
  N                  3.13203364    4.88891811    4.86017069
  N                  4.41614536    6.39243688    3.61722930
  C                  4.06455509    5.08156078    3.87216675
  C                  3.99019119    7.48412061    4.31476378
  C                  3.26108613    7.19962350    5.59032474
  C                  2.60656705    5.86093941    5.67109699
  H                  2.86290309    4.11746664    4.98744525
  H                  4.99506469    6.53336424    2.97784697
  H                  3.91898313    7.20780232    6.28834462
  H                  2.63762500    7.85329996    5.80293441
K_POINTS automatic
   1 1 1   1 1 1


-- 
------------------------------------------------------
Carlo Nervi carlo.nervi at unito.it Tel:+39 011 6707507/8
Fax: +39 011 6707855   -   Dipartimento di Chimica IFM
via P. Giuria 7, 10125 Torino, Italy
http://lem.ch.unito.it/