OpenMP C

If you have not done yet, download the Sample files by:

git clone https://hidekiCCS:@bitbucket.org/hidekiCCS/hpc-workshop.git

Hello World

hpc-workshop/SimpleExample/C/hello_OMP

/*
  hellp_omp.c: display a message on the screen
*/
#include <stdio.h>
#include <omp.h>
 
int main () {
  int id, nthreads;
  printf("C Start\n");
#pragma omp parallel private(id)
  {
    id = omp_get_thread_num();
    printf("hello from %d\n", id);
#pragma omp barrier
    if ( id == 0 ) {
      nthreads = omp_get_num_threads();
      printf("%d threads said hello!\n",nthreads);
    }
  }
  printf("End\n");
}

Compile with GNU C

gcc hello_omp.c -fopenmp

Compile with Intel C

module load intel-psxe
icc hello_omp.c -openmp

Example of Jobscript

#!/bin/bash
#SBATCH --qos=normal            # Quality of Service
#SBATCH --job-name=helloC_OMP   # Job Name
#SBATCH --time=00:10:00         # WallTime
#SBATCH --nodes=1               # Number of Nodes
#SBATCH --ntasks-per-node=1     # Number of tasks (MPI processes)
#SBATCH --cpus-per-task=4       # Number of processors per task OpenMP threads()
#SBATCH --gres=mic:0            # Number of Co-Processors

module load intel-psxe

pwd

echo "DIR=" $SLURM_SUBMIT_DIR
echo "TASKS_PER_NODE=" $SLURM_TASKS_PER_NODE
echo "NNODES=" $SLURM_NNODES
echo "NTASKS" $SLURM_NTASKS
echo "JOB_CPUS_PER_NODE" $SLURM_JOB_CPUS_PER_NODE
echo $SLURM_NODELIST

export OMP_NUM_THREADS=$SLURM_CPUS_PER_TASK
./a.out