[Pw_forum] Parallel efficiency problem

[lihm]

Dear all,

   I am a fresh user of PWscf. I run the parallel calculations to have a test.
A single process test is OK:     

PWSCF        :  5m40.68s CPU time,     6m 0.14s wall time

However, I found that the walltime is too long for parallel calculations:

     PWSCF        :  1m 4.86s CPU time,    32m53.67s wall time 

I am sure that the CPU are not busy, or influenced by other jobs. 

The running command is:

/usr/local/mpich/bin/mpirun -np 4 -machinefile nodelist /bin/pw.x < ZnO.scf.inp > ZnO.scf.out

My input file is

 &CONTROL
                 calculation = 'scf' ,
                restart_mode = 'from_scratch' ,
                      outdir = './' ,
                      wfcdir = '/tmp/' ,
                  pseudo_dir = './' ,
                      prefix = 'ZnO' ,
                     disk_io = 'minimal' ,
                     tstress = .true. ,
                     tprnfor = .true. ,
 /
 &SYSTEM
                       ibrav = 4,
                   celldm(1) = 6.213,
                   celldm(3) = 1.610,
                         nat = 4,
                        ntyp = 2,
                     ecutwfc = 40 ,
                     ecutrho = 400 ,
 /
 &ELECTRONS
                 mixing_mode = 'plain' ,
                 mixing_beta = 0.7 ,
             diagonalization = 'david' ,
 /
ATOMIC_SPECIES
   Zn   65.39200  Zn.pbe-van.UPF 
    O   16.00000  O.pbe-rrkjus.UPF 
ATOMIC_POSITIONS crystal 
   Zn      0.666666667    0.333333333    0.000000000    
   Zn      0.333333333    0.666666667    0.500000000    
    O      0.666666667    0.333333333    0.380000000    
    O      0.333333333    0.666666667    0.880000000    
K_POINTS automatic 
  16 16 8   0 0 0 

Can anyone help me to fix the problem? Thank you.

    Best wishes!

                           Haiming Li
                           2008-07-29
 				
--------------
Haiming Li
Beijing Synchrotron Radiation Facility
Institute of High Energy Physics
Chinese Academy of Sciences
19 Yu Quan Lu, 100049 Beijing, P.R. China
Tel: 0086+10 8823 6437  /  0086+135 8190 2824                
E-mail:lihm at ihep.ac.cn