OpenMP

#include <omp.h>
#include <stdio.h>
#include <unistd.h>

int main (int argc, char **argv)
{
    int nthreads, tid;
    char host[32];

    #pragma omp parallel private(nthreads, tid, host)
    {
        tid = omp_get_thread_num();
        gethostname(host,32);
        printf("Hello world from the thread %d running on %s\n", tid,host);
        if (tid == 0) {
            nthreads = omp_get_num_threads();
            printf("[Thread 0 say: there are %d threads]\n", nthreads);
        }
    }
}

gcc -fopenmp -O2 omp_hello.c -o omp_hello.out

omp_hello.out : omp_hello.c
        gcc -fopenmp -O2 -o $@ omp_hello.c

#!/bin/sh
#PBS -l walltime=00:00:30
#PBS -l select=1:ncpus=4:ompthreads=4

cd $PBS_O_WORKDIR
echo "OMP_NUM_THREADS = $OMP_NUM_THREADS"
echo
./omp_hello.out

OMP_NUM_THREADS = 4

Hello world from the thread 3 running on cn101
Hello world from the thread 0 running on cn101
[Thread 0 say: there are 4 threads]
Hello world from the thread 1 running on cn101
Hello world from the thread 2 running on cn101

    program hello
    integer id, nthrds
    integer omp_get_thread_num, omp_get_num_threads
!$omp parallel private(id)
    id = omp_get_thread_num()
    print *, 'hello world from thread', id
!$omp barrier
    if ( id .eq. 0 ) then
        nthrds = omp_get_num_threads()
        print *, 'there are', nthrds, 'threads'
    end if
!$omp end parallel
    end

gfortran -O2  -fopenmp -o omp_hello.out omp_hello.f90

omp_hello.out : omp_hello.f90
        gfortran -O2  -fopenmp -o $@ omp_hello.f90