Re-starting a calculation

["John J. Rehr" <jjr@leonardo.phys.washington.edu>]

Paula Harkins asked about restarting a FEFF8 calculation:

>I am using Feff8 (ver 8.1) and wondered if there was any way to restart a 
>calculation from the point that it was stopped at rather than having to 
>wait for the whole calculation to run again. (I share my computer with 
>several other users!) Any ideas?

  At present this can only be done module by module. For example if a 
calculation stops during  the 3rd module [FMS], it is not necessary to
rerun the first two modules and one can restart the calculation with

CONTROL 0 0 1 1 1 1

You can check that a module has finished by looking at the last line
in logn.dat. For example, when the potentials have been calculated the
last line should say:

Done with module 1: potentials.

  What else can be done?

  If you do want to stop a job temporarily, you can use the ctrl-z command
in unix to stop a job and then restart later with the command fg.


  Several things can be done to optimize the speed to avoid the need for
stopping/restarting:

i)  For XANES calculations, the time goes up as [N(lmax+1)**2]**3,
so you should keep the cluster size as small as you can get away
with without sacrificing accuracy [typically 30-40 atoms] and
with default lmax [set lmax = -1 in POTENTIALS].

ii)  For the FMS part, if you have FEFF8.2 the calculations go faster with the
Lanczos algorithm.

  We'll look into the possibility of restarting a FEFF8 calculation mid 
module. Certainly some band structure codes allow one to restart during
the SCF loop.

   Cheers,
   John Rehr