User's Guide

Example 3 - Valid Fortran SMP Source File

!*****************************************************************
!* This example uses a PARALLEL construct and a DO construct     *
!* to calculate the value of pi.                                 *
!*****************************************************************
      program compute_pi
      integer n, i
      real *8 w, x, pi, f, a
      f(a) = 4.d0 /(1.d0 + a*a)  !! function to integrate
 
      pi = 0.0d0
!$OMP PARALLEL private(x, w, n), shared(pi)
      n = 10000                     !! number of intervals
      w = 1.0d0/n                   !! calculate the interval size
!$OMP DO reduction(+: pi)
      do i = 1, n
         x = w * (i - 0.5d0)
         pi = pi + f(x)
      enddo
!$OMP END DO
!$OMP END PARALLEL
      print *, "Computed pi = ", pi
     end