[slurm-users] About seff command

[xiaojinghu93 at 163.com]

Hi guys,
I would like to calculate the CPU efficiency and Memory efficiency of slurm jobs. I know that the “seff” command is for this. I’d like to do the same job on my own. 
When I was studying the source code of the seff command, I saw the code below:

my $ncpus = 1;
if (exists $job->{'alloc_cpus'}) {
    $ncpus = $job->{'alloc_cpus'};
} else {
    if (exists $job->{'tres_alloc_str'}) {
	$ncpus = Slurmdb::find_tres_count_in_string($job->{'tres_alloc_str'}, TRES_CPU);
    }
}

I am wondering under what circumstance would the “alloc_cpus” field for a job to be empty while having corresponding value in AllocCPU field?

Very grateful for any help.
Thank you!