Each cluster imposes a wall clock limit on the running time of a job (e.g., on Tiger it is 6 days). If you need to run a job for much longer than this time then you should consider using the job dependency technique described below.
To use job dependencies in this way your application must be capable of writing a checkpoint file at the end of each job step and it must be able to figure out which checkpoint file to read at the start of each job step. If your application does not meet these two requirements then one can typically write scripts to deal with it.
For the first step, run your job as usual: $ sbatch job.slurm. Make sure it finishes before the time limit and make
sure you write a checkpoint file. Then modify your application script to automatically read the checkpoint file at the start of each job step, for example, in pseudocode:
// read newest checkpoint file at start
// do work
// write checkpoint file at end
Modify the Slurm script by adding this line: --dependency=singleton
#!/bin/bash
#SBATCH --job-name=MyLongJob # create a short name for your job
#SBATCH --nodes=1 # node count
#SBATCH --ntasks=1 # total number of tasks across all nodes
#SBATCH --cpus-per-task=1 # cpu-cores per task (>1 if multi-threaded tasks)
#SBATCH --mem-per-cpu=4G # memory per cpu-core (4G is default)
#SBATCH --time=72:00:00 # total run time limit (HH:MM:SS)
#SBATCH --dependency=singleton # job dependency
#SBATCH --mail-type=begin # send email when job begins
#SBATCH --mail-type=end # send email when job ends
#SBATCH --mail-user=<YourNetID>@princeton.edu
myprogram <args>
The second and additional job steps can then be submitted. The --job-name value must be the same for each submission. Each step will wait for the one before it since each is waiting for MyLongJob to finish. This is how singleton works. The following will produce a total of 5 jobs steps.
$ sbatch job.slurm # step 2
$ sbatch job.slurm # step 3
$ sbatch job.slurm # step 4
$ sbatch job.slurm # step 5
Of course, with our previous alias for sbatch job.slurm one could equivalently enter sb four times. Read more about job dependencies on the Slurm website. Note that you could also include the singleton job dependency for the very first submission (i.e., step 1).
There is a specific example for LAMMPS here.