Request the maximum ntasks be invoked on each node. Meant to be used with the --nodes option.
This is related to --cpus-per-task=ncpus, but does not require knowledge of the actual number of
cpus on each node. In some cases, it is more convenient to be able to request that no more than a
specific number of tasks be invoked on each node. Examples of this include submitting a hybrid
MPI/OpenMP app where only one MPI "task/rank" should be assigned to each node while allowing the
OpenMP portion to utilize all of the parallelism present in the node, or submitting a single
setup/cleanup/monitoring job to each node of a pre-existing allocation as one step in a larger job
-x, --exclude=<host1,host2,... or filename>
Request that a specific list of hosts not be included in the resources allocated to this job. The
host list will be assumed to be a filename if it contains a "/"character.
Specify a list of constraints. The constraints are features that have been assigned to the nodes
by the slurm administrator. The list of constraints may include multiple features separated by
ampersand (AND) and/or vertical bar (OR) operators. For example: --constraint="opteron&video" or
--constraint="fast|faster". In the first example, only nodes having both the feature "opteron"
AND the feature "video" will be used. There is no mechanism to specify that you want one node
with feature "opteron" and another node with feature "video" in case no node has both features.
If only one of a set of possible options should be used for all allocated nodes, then use the OR
operator and enclose the options within square brackets. For example:
"--constraint=[rack1|rack2|rack3|rack4]" might be used to specify that all nodes must be allocated
on a single rack of the cluster, but any of those four racks can be used. A request can also
specify the number of nodes needed with some feature by appending an asterisk and count after the
feature name. For example "srun --nodes=16 --constraint=graphics*4 ..." indicates that the job
requires 16 nodes at that at least four of those nodes must have the feature "graphics."
Constraints with node counts may only be combined with AND operators. If no nodes have the
requested features, then the job will be rejected by the slurm job manager. This option is used
for job allocations, but ignored for job step allocations.