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Restart

This keyword restarts a previously-failed job. This method is primarily intended for long jobs that involve sufficiently large amounts of intermediate data, so that saving the restart data in the checkpoint file would make the checkpoint file unmanageably enormous, which would defeat the purpose of having a checkpoint file separate from the read-write file. This procedure depends on naming the read-write file so that it will be saved if the job terminates abnormally, and then using it to restart.

For example, in a frequency calculation you would include following Link 0 commands:

%RWF=myrwf
%NoSave
%Chk=mychk
#P Freq …

input continues…

By default, any file which is named with a % line is retained when the job finishes. The %NoSave after the %RWF overrides this default, so that the read-write file will still be deleted if the job finishes normally (but will be left behind if the job terminates early).

Be careful about these points:

  • The checkpoint file is often useful after the job finishes, so one typically places it after the %NoSave.
  • The read-write file may be huge and should be put on a suitable file system. For example, the checkpoint file can be placed in a regular user directory, which might have only a moderate amount of free space and/or be NFS-mounted. However, the read-write file for a job large enough to be worth restarting should be on a large, local scratch file system.
  • A restartable job is one for which execution was stopped before completion. Jobs that finish with an error message such as convergence failure or exceeding number of optimization steps require user intervention.

Analytic frequency calculations, including properties like ROA and VCD with ONIOM; CCSD and EOM-CCSD calculations; NMR; Polar=OptRot; CID, CISD, CCD, QCISD and BD energies. Calculations that compute multiple geometries, such as geometry optimizations, IRCs, and numerical frequency calculations, are better just restarted off the checkpoint file as before.

The following input file will restart a job set up as described above:

%RWF=myrwf
%NoSave
%Chk=mychk
#P Restart

No other keywords are required in the route section, and no other input is needed.


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