! Summation in the correct order using CAF
IMPLICIT NONE
REAL, DIMENSION[*] :: PART_SUM, TIME1, TIME2
REAL, EXTERNAL :: WTIME
REAL :: WHOLE_SUM, TIME_SUM, TIME3, TIME4
Integer :: NUMBER, I, N

!call caf_init()
call sync_images()
N = num_images()     ! = number of processors

NUMBER = 2000000     ! = total number of elements to sum
PART_SUM = 0.0
call sync_images()

TIME3 = WTIME()      ! Wall clock for the start
call cpu_time(TIME1) ! CPU  clock for the start

do I = NUMBER + 1 - this_image(), 1, -N ! Backwards
!  Summation of each, each other, each third, ... element 
!  on the respective processor if N = 1, 2, 3, ... 
   PART_SUM = PART_SUM + 1.0/REAL(I)**2
end do

call cpu_time(TIME2) ! CPU  clock for the finish
TIME4 = WTIME()      ! Wall clock for the finish

call sync_images()
! Assemble the results on processor 1
if ( this_image() == 1 ) then
   WHOLE_SUM = 0.0
   TIME_SUM = 0.0
   do I = 1, N
      WHOLE_SUM = WHOLE_SUM + PART_SUM[I]
      TIME_SUM = TIME_SUM + TIME2[I] - TIME1[I]
   end do
   write(*,10) N, WHOLE_SUM, TIME_SUM, TIME4 - TIME3
10 FORMAT(2X,'NUMBER OF PROCESSORS',5X,'WHOLE_SUM',9X, &
&  'TOTAL CPU TIME',5X, 'WALL CLOCK TIME',/ &
&  5X,I5,15X,F16.12,F12.6,7X,F12.6)
end if

end