program main

c*********************************************************************72
c
cc PRIME computes the sum of the prime numbers between 2 and 100,000.
c
c  Discussion:
c
c    This program is very close to being an MPI program already.
c
c    The calculation has been split up among P processes, each of
c    which is given a range to work in, and each of which returns a
c    partial sum and CPU time.
c
c    Modify the program so that it runs under MPI.
c
      implicit none

      integer i
      integer j
      integer id
      integer id_n_hi
      integer id_n_lo
      double precision id_time
      integer id_total
      integer n_hi
      parameter ( n_hi = 100000 )
      integer n_lo
      parameter ( n_lo = 2 )
      integer p
      parameter ( p = 10 )
      logical prime
      double precision wtime
      double precision wtime_total
      double precision wtime1
      double precision wtime2
      integer total

      total = 0
c
c  We pretend there are P processes.
c  We divide the range [N_LO,N_HI] into P roughly equal subintervals.
c  We ask process ID to check the ID-th subinterval and return the
c  total in that range.
c
      write ( *, '(a)' ) ' '
      write ( *, '(a)' ) 
     &  '        ID      N_LO      N_HI         TOTAL        TIME'
      write ( *, '(a)' ) ' '

      do id = 0, p - 1

        id_n_lo = ( ( p - id     ) *   n_lo 
     &            + (     id     ) * ( n_hi + 1 ) ) 
     &            / ( p          )

        id_n_hi = ( ( p - id + 1 ) *   n_lo 
     &            + (     id + 1 ) * ( n_hi + 1 ) ) 
     &            / ( p          ) - 1

        id_total = 0

        do i = id_n_lo, id_n_hi

          prime = .true.

          do j = 2, i - 1
            if ( mod ( i, j ) .eq. 0 ) then
              prime = .false.
              go to 10
            end if
          end do

          if ( prime ) then
            id_total = id_total + i
          end if

10      continue

        end do

        write ( *, '(2x,i8,2x,i8,2x,i8,2x,i12,2x,g14.6)' ) 
     &    id, id_n_lo, id_n_hi, id_total

        total = total + id_total

      end do

      write ( *, '(a)' ) ' '
      write ( *, '(2x,a8,2x,i8,2x,i8,2x,i12,2x,g14.6)' ) 
     &  '   Total', n_lo, n_hi, total

      stop
      end