slurm-job-submission-and-execution.md

# Slurm Job Submission and Execution

## Introduction

[Slurm][1] workload manager is used to allocate and access Barbora cluster and Complementary systems resources.

## Getting Partitions Information

Display partitions/queues

```console
$ sinfo -s
PARTITION    AVAIL  TIMELIMIT   NODES(A/I/O/T) NODELIST
qcpu*           up 2-00:00:00      1/191/0/192 cn[1-192]
qcpu_biz        up 2-00:00:00      1/191/0/192 cn[1-192]
qcpu_exp        up    1:00:00      1/191/0/192 cn[1-192]
qcpu_free       up   18:00:00      1/191/0/192 cn[1-192]
qcpu_long       up 6-00:00:00      1/191/0/192 cn[1-192]
qcpu_preempt    up   12:00:00      1/191/0/192 cn[1-192]
qgpu            up 2-00:00:00          0/8/0/8 cn[193-200]
qgpu_biz        up 2-00:00:00          0/8/0/8 cn[193-200]
qgpu_exp        up    1:00:00          0/8/0/8 cn[193-200]
qgpu_free       up   18:00:00          0/8/0/8 cn[193-200]
qgpu_preempt    up   12:00:00          0/8/0/8 cn[193-200]
qfat            up 2-00:00:00          0/1/0/1 cn201
qdgx            up 2-00:00:00          0/1/0/1 cn202
qviz            up    8:00:00          0/2/0/2 vizserv[1-2]
```

## Getting Job Information

Show jobs

```console
$ squeue --me
             JOBID PARTITION     NAME     USER ST       TIME  NODES NODELIST(REASON)
               104   qcpu    interact    user   R       1:48      2 cn[101-102]
```

Show job details for specific job

```console
$ scontrol -d show job JOBID
```

Show job details for executing job from job session

```console
$ scontrol -d show job $SLURM_JOBID
```

## Running Interactive Jobs

Run interactive job

```console
 $ salloc -A PROJECT-ID -p qcpu
```

Run interactive job, with X11 forwarding

```console
 $ salloc -A PROJECT-ID -p qcpu --x11
```

!!! warning
    Do not use `srun` for initiating interactive jobs, subsequent `srun`, `mpirun` invocations would block forever.

## Running Batch Jobs

Run batch job

```console
 $ sbatch ./script.sh
```

```shell
#!/usr/bin/bash
#SBATCH -J MyJobName
#SBATCH -A OPEN-00-00
#SBATCH -N 4
#SBATCH --ntasks-per-node 36
#SBATCH -p qcpu
#SBATCH -t 12:00:00

ml OpenMPI/4.1.4-GCC-11.3.0

srun hostname | uniq -c
`

Useful command options (salloc, sbatch, srun)

* -N, --nodes
* --tasks-per-node
* -n, --ntasks
* -c, --cpus-per-task

## Slurm Job Environment Variables

Slurm provides useful information to the job via environment variables. Environment variables are available on all nodes allocated to job when accessed via Slurm supported means (srun, compatible mpirun).

See all Slurm variables

```
set | grep ^SLURM
```

### Useful Variables

| variable name | description | example |
| ------ | ------ | ------ |
| SLURM_JOBID | job id of the executing job| 593 |
| SLURM_JOB_NODELIST | nodes allocated to the job | cn[101-102] |
| SLURM_JOB_NUM_NODES | number of nodes allocated to the job | 2 |
| SLURM_STEP_NODELIST | nodes allocated to the job step | cn101 |
| SLURM_STEP_NUM_NODES | number of nodes allocated to the job step | 1 |
| SLURM_JOB_PARTITION | name of the partition | qcpu |
| SLURM_SUBMIT_DIR | submit directory | /scratch/project/open-xx-yy/work |

See [Slurm srun documentation][2] for details.

Get job nodelist

```
$ echo $SLURM_JOB_NODELIST
cn[101-102]
```

Expand nodelist to list of nodes.

```
$ scontrol show hostnames $SLURM_JOB_NODELIST
cn101
cn102
```

## Modifying Jobs

```
$ scontrol update JobId=JOBID ATTR=VALUE
```

for example

```
$ scontrol update JobId=JOBID Comment='The best job ever'
```

## Deleting Jobs

```
$ scancel JOBID
```

[1]: https://slurm.schedmd.com/
[2]: https://slurm.schedmd.com/srun.html#SECTION_OUTPUT-ENVIRONMENT-VARIABLES