[slurm-users] issue with --cpus-per-task=1

[Benjamin Glaessle]

Hello all!

we are using slurm 20.11.8 with
> SelectType              = select/cons_tres
> SelectTypeParameters    = CR_CORE_MEMORY
and nodes with enable hyperthreading, e.g.
> NodeName=slurm-node?? NodeAddr=192.?? Procs=72 Sockets=2 CoresPerSocket=18 ThreadsPerCore=2 RealMemory=...

when launching jobs on these nodes with --cpus-per-task 1 they execute 
twice:
 > $ srun --cpus-per-task 1 echo foo
 > foo
 > foo

digging deeper I found
> $ srun --cpus-per-task 1 env | grep -i tasks
> SLURM_NTASKS=2
> SLURM_TASKS_PER_NODE=2
> SLURM_STEP_NUM_TASKS=2
> SLURM_STEP_TASKS_PER_NODE=2
> SLURM_NTASKS=2
> SLURM_TASKS_PER_NODE=2
> SLURM_STEP_NUM_TASKS=2
> SLURM_STEP_TASKS_PER_NODE=2

whereas `scontrol show job 12345 | grep -i -e numtasks -e numcpus` for 
both "env" and "echo" job gives
> NumNodes=1 NumCPUs=2 NumTasks=1 CPUs/Task=1 ReqB:S:C:T=0:0:*:*

A test node without ThreadsPerCore=2 behaves "normally".
Also
 > $ srun -n1 --cpus-per-task 1 echo foo
 > foo
resolves the problem.

This seems like a bug to me.
Can this be reproduced (on newer versions)?

Can this somehow be avoided by setting a default number of tasks or some 
other (partition) parameter? Sorry for asking but I couldn't find 
anything in the documentation.

Let me know if you need more information.

Best Regards, Benjamin