Most codes permit a checkpoint file to be created so that one's job can be continued from the point shortly before it failed. Since QE 5.1 restarting from an arbitrary point of the code is no more supported. Instead it is possible to write out only one checkpoint file at a user specified time.

Please see and look for restart_mode and max_seconds in the QE documentation. https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm60

If your QE job is running on one node, the smp queue, then the maximum walltime is 96 hours, while for 2 nodes or more on the normal queue the maximum walltime is 48 hours.

If you believe your job will require a shorter time than the maximum walltimes, then it is important to use this fact. You also may believe that you job may not complete in the 48 or 96 hours. You can then make a decision on what max_seconds value to use in your QE input file. For example:

1. You believe your job will complete within 20 hours for example, or that around 20 hours is a vital point in the calculation where you believe restarting from is important, or that you've seen your job fail previously after 20 hours:

Set your PBS job walltime greater than 20 hours (21 hours for example), and choose max_seconds equivalent to 20 hours.

20 hours = 20 x 60 x 60 = 72 000 seconds max_seconds=72000 restart_mode ='restart'

2. Your job won't complete in 48 hours on normal queue, then choose a time less than 48 hours such as 47 hours:

47 hours = 47 x 60 x 60 = 169 200 seconds max_seconds=169200 restart_mode ='restart'

2. Your job won't complete in 96 hours on smp queue, then choose a time less than 96 hours such as 95 hours:

95 hours = 95 x 60 x 60 = 342 000 seconds max_seconds=342000 restart_mode ='restart'