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subroutine initialize_array(n, a)
use omp_lib
implicit none
integer, intent(in) :: n
real, dimension(n), intent(out) :: a
integer :: i
!$omp parallel
!$omp do
do i = 1, n
a(i) = 12.91
end do
!$omp end do
!$omp end parallel
print *, a(1), a(n)
end subroutine
subroutine parallel_sum(n, a)
use omp_lib
implicit none
integer, intent(in) :: n
real, dimension(n), intent(in) :: a
integer :: i
real :: sum
sum = 0.0
!$omp parallel do reduction(+:sum)
do i = 1, n
sum = sum + a(i)
end do
!$omp end parallel do
print *, 'Sum = ', sum
! here we have precision error both with gfortran and lfortran
! setting different number of threads leads to different results
! but in any case output of gfortran and lfortran is the same
if (abs(sum - 12905576.0) > 1e-8) error stop
end subroutine
program openmp_14
use omp_lib
integer, parameter :: n = 1000000
real, dimension(n) :: a
call omp_set_num_threads(8)
call initialize_array(n, a)
call parallel_sum(n, a)
print *, a(1), a(n)
end program
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