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program openmp_54
use omp_lib
implicit none
integer, parameter :: N = 1000
integer :: i, tid
integer :: total_sum
integer :: partial_sum
!$omp parallel shared(total_sum) private(i, partial_sum, tid)
tid = omp_get_thread_num()
partial_sum = 0
total_sum = 0
!$omp barrier
!$omp do
do i = 1, N
partial_sum = partial_sum + i
end do
!$omp end do
! Critical update to the shared total_sum
!$omp critical
total_sum = total_sum + partial_sum
print *, "Thread ", tid, " added partial_sum ", partial_sum
!$omp end critical
!$omp barrier
!$omp single
if (total_sum /= N*(N+1)/2) then
print *, "ERROR: total_sum = ", total_sum, " expected = ", N*(N+1)/2
error stop
else
print *, "Success! total_sum = ", total_sum
end if
!$omp end single
!$omp end parallel
end program openmp_54
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