[Pw_forum] Does not disk_io='low' work with calculation='bands'?

[GAO Zhe]

Dear QE Developer and Users:
I met a problem while calculating band structure. My in put file is like this:
cat >XXX.scf.in <<EOF
&control
     calculation = 'scf' ,
     prefix = 'XXX' ,
     outdir= '$TempDIR/' ,
     pseudo_dir = '$PseudoDIR/' ,
     etot_conv_thr = 1.0d-9 ,
     restart_mode = 'from_scratch' ,
     disk_io = 'low' ,
/
&system
     ibrav = 2 ,
     celldm(1) = *** ,
     nat = 2 ,
     ntyp = 2 ,
     ecutwfc = 42.5 ,
     ecutrho = 400 ,
     occupations = 'smearing' ,
     smearing = 'mp' ,
     degauss = 0.015 ,
/
&electrons
     conv_thr = 1.0d-9 ,
     startingpot = 'atomic' ,
     startingwfc = 'atomic+random' ,
     diagonalization = 'david' ,
     mixing_mode = 'plain' ,
     mixing_beta = 0.7 ,
/
ATOMIC_SPECIES
 *******
ATOMIC_POSITIONS crystal
  *******
K_POINTS
 10
  0.0000000   0.0000000   0.0000000  0.0160000
***********
  0.6000000  -0.2000000   1.0000000  0.3840000
EOF
pw.x <XXX.scf.in >XXX.scf.out
cat >XXX.band.in <<EOF
&control
     calculation = 'bands' ,
     prefix = 'XXX' ,
     outdir= '$TempDIR/' ,
     pseudo_dir = '$PseudoDIR/' ,
     etot_conv_thr = 1.0d-9 ,
     disk_io = 'low' ,
/
&system
     ibrav = 2 ,
     celldm(1) = *** ,
     nat = 2 ,
     ntyp = 2 ,
     ecutwfc = 42.5 ,
     ecutrho = 400 ,
     nbnd = 12 ,
/
&electrons
     diagonalization = 'david' ,
/
ATOMIC_SPECIES
 ******
ATOMIC_POSITIONS crystal
  ******
K_POINTS
 28
   0.0 0.0 0.0 1.0
*******
   0.5 0.5 0.5 1.0
EOF
pw.x <XXX.band.in >XXX.band.out
Then, I got an error frompw.x and process stopped. The error was:
        Each <psi_i|beta_j> matrix      0.01 Mb     (     52,  12)
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     from davcio : error #        99
     error while reading from file
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     stopping ...
However, after I removeddisk_io = 'low' in SCF calculation, non-SCF calculation can run without any problem.
I checkedXXX.save/charge-density.dat, the files' size seemed same when disk_io equal to 'low' and 'default'. Is this phenomenon meansdisk_io = 'low' cannot be used duringcalculation='bands' and 'nscf'? I am afraiddisk_io = 'default' would lower speed when model was huge~

--
GAO Zhe
CMC Lab, MSE, SNU, Seoul, S.Korea
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