Example Fortran: Performing a Sum

call MPI_COMM_RANK( comm, rank, ierr )

if (rank .eq. 0) then

read *, n

end if

call MPI_BCAST(n, 1, MPI_INTEGER, 0, comm, ierr )

# Each process computes its range of numbers to sum

lo = rank*n+1

hi = lo+n-1

sum = 0.0d0

do i = lo, hi

sum = sum + 1.0d0 / i

end do

call MPI_REDUCEALL( sum, sumout, 1, MPI_DOUBLE,

& MPI_ADD_DOUBLE, comm, ierr)

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