[user@computer dir]$ export OMP_NUM_THREADS=2 [user@computer dir]$ gfortran pp_omp_ex4.f90 -o pp_omp_ex4 [user@computer dir]$ ./pp_omp_ex4 i,a(i),thread number 1 2 0 2 4 0 3 6 0 4 8 0 5 10 0 6 12 0 7 14 0 [user@computer dir]$ gfortran -fopenmp pp_omp_ex4.f90 -o pp_omp_ex4 [user@computer dir]$ ./pp_omp_ex4 i,a(i),thread number 1 2 0 2 4 0 3 6 0 4 8 0 5 10 1 6 12 1 7 14 1 [user@computer dir]$