Programming/OpenMP

Programming Details

OpenMP is designed for multi-processor/core, shared memory machines. The underlying architecture can be shared memory UMA or NUMA.

It is an Application Program Interface (API) that may be used to explicitly direct multi-threaded, shared memory parallelism. Comprised of three primary API components:

• Compiler Directives
• Runtime Library Routines
• Environment Variables

OpenMP compiler directives are used for various purposes:

• Spawning a parallel region
• Dividing blocks of code among threads
• Distributing loop iterations between threads
• Serializing sections of code
• Synchronization of work among threads

Usage Examples

#!/bin/bash

#SBATCH -J openmpi-single-node
#SBATCH -N 1
#SBATCH --ntasks-per-node 28
#SBATCH -D /home/user/CODE_SAMPLES/OPENMP
#SBATCH -o %N.%j.%a.out
#SBATCH -e %N.%j.%a.err
#SBATCH -p compute
#SBATCH --exclusive

echo $SLURM_JOB_NODELIST

module purge
module load gcc/4.9.3

export I_MPI_DEBUG=5
export I_MPI_FABRICS=shm:tmi
export I_MPI_FALLBACK=no

/home/user/CODE_SAMPLES/OPENMP/demo

[username@login01 ~]$ sbatch demo.job
Submitted batch job 289552