[slurm-users] What is the complete logic to calculate node number in job_submit.lua

[Ole Holm Nielsen]

Hi Loris,

On 9/26/22 12:51, Loris Bennett wrote:
>> When designing restriction in job_submit.lua, I found there is no member in job_desc struct can directly be used to determine the node number finally allocated to a job. The job_desc.min_nodes seem to
>> be a close answer, but it will be 0xFFFFFFFE when user not specify –node option. Then in such case we think we can use job_desc.num_tasks and job_desc.ntasks_per_node to calculate node number.
>> But again, we find ntasks_per_node may also be default value 0xFFFE if user not specify related option.
>>
>> So what is the complete and elegant way to predict the job node number in job_submit.lua in all case, no matter how user write their submit options?
> 
> I don't think you can expect to know the node(s) a job will eventually
> run on at submission time.  How would this work?  Resources will become
> available earlier than Slurm expects, if jobs finish before the given
> time-time (or if they crash).  If your are using fairshare, jobs can be
> scheduled which have a higher priority than the currently waiting jobs.
> 
> What is your use-case for needing to know the node the job will run on?

I think he meant the *number of nodes*, and not the *hostnames* of the 
compute nodes selected by Slurm at a later time.

/Ole