#Fortran

Copy this into loops.F

      program main
      use omp_lib
      implicit none

      integer i, thread_id, nloops

C$OMP PARALLEL PRIVATE(thread_id, nloops)

      thread_id = omp_get_thread_num()
      nloops = 0

C$OMP DO
      do 100 i=1,1000
          nloops = nloops + 1
100   continue

      print *,"Thread ",thread_id," performed ",
     .        nloops," iterations."

C$OMP END PARALLEL

      end

The new directive in this code is $OMP DO. This tells the compiler that the do loop directly below this pragma can be run in parallel by the team of threads. In this case, the only work performed in each iteration is increasing the thread private counter of the number of times that the loop has been performed (each thread in the team has its own copy of nloops because it is specified as PRIVATE as part of the !OMP PARALLEL directive). By doing this, each thread in the team counts up the number of times that it has performed the loop.

You can compile this program using one of these commands (choose one for the compiler you wish to use);

• gfortran : gfortran -fopenmp loops.f -o loops
• ifort : ifort -openmp loops.f -o loops -cxxlib-icc
• pgf77 : pgf77 -mp loops.f -o loops

This will produce the executable, loops.

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