OpenMP on CPU CLX

Owned by Lewin Stein (Unlicensed)
Last updated: Okt. 11, 2024 by Matthias Laeuter
1 min read

Code execution

Per default our hardware supports hyperthreading, allowing you start 192 processes on Cascade Lake machines (*96 partitions) and 80 on Skylake machines.

Hyperthreading active, 80/192 Processes per Node will be started 
#!/bin/bash
#SBATCH -N 4

cpus_per_node=${SLURM_JOB_CPUS_PER_NODE%\(*}
export OMP_NUM_THREADS=$(($cpus_per_node*$SLURM_JOB_NUM_NODES)) 

# Run multi-threaded application ./yourexe

Note that more than one node, as in the example set with `-N 4` can only be used with a hybrid MPI-OpenMP job. For pure OpenMP programs, one '-N 1' is meaningful.

Hyperthreading disabled, 96 processes per node are started. 
#!/bin/bash
#SBATCH -N 4
#SBATCH --tasks-per-node 96

tasks_per_node=${SLURM_TASKS_PER_NODE%\(*}
export OMP_NUM_THREADS=$(($tasks_per_node*$SLURM_JOB_NUM_NODES))

# Run multi-threaded application ./yourexe