! A driver model code for Multi-Process Handshaking utility
! to facilitate a plug & play style programming using single executable.
! each processor only execute one component model once. 
! Written by Yun (Helen) He and Chris Ding, NERSC/LBNL, December 2000.

      program main
      use MPH_module
      implicit none

      integer myProc_global, global_sum
      integer comm_cpl_pop, myProc_joined, join_sum
      character*10 c2o(30), c2o_yes(30)
      integer a2c(100), a2c_yes(100)
      integer ocean_comm, atmos_comm, coupler_comm
      integer i, nsteps
      parameter (nsteps = 1)

! --- call the setup routine with the component model names
      call MPH_setup_SE_overlap ("atmosphere", "ocean", "coupler")


! ---- call each component in the order and times you like ----

      if (PE_in_component("ocean", ocean_comm)) then
         call pop2_2(ocean_comm) 
      endif

      do i = 1, nsteps
         if (PE_in_component("atmosphere", atmos_comm)) then
            call ccm3_8(atmos_comm) 
         endif
         if (PE_in_component("coupler", coupler_comm)) then
            call cpl5_1(coupler_comm) 
         endif
      enddo 
 

! --- some global operations ----
      call MPI_COMM_RANK (MPI_COMM_WORLD, myProc_global, ierr)
      call MPI_ALLREDUCE (myProc_global, global_sum, 1, 
     &                    MPI_INTEGER, MPI_SUM, MPI_COMM_WORLD, ierr)
      if (myProc_global == 0) then
         write(*,*)' sum of global ranks in world is ', global_sum
      endif


! ---- create a joined communicator for coupler and ocean ----
! ---- and do some global reduction in the joined communicator ---

      call MPH_COMM_JOIN ("coupler", "ocean", comm_cpl_pop)

      if (PE_in_component("coupler", coupler_comm) .or.
     &    PE_in_component("ocean", ocean_comm)) then 
         call MPI_COMM_RANK (comm_cpl_pop, myProc_joined, ierr)
         write(*,*)'myProc_joined=', myProc_joined
         call MPI_ALLREDUCE (myProc_joined, join_sum, 1, MPI_INTEGER,
     &                       MPI_SUM, COMM_cpl_pop, ierr)
         if (myProc_joined == 0) then
            write(*,*)' sum of joined ranks in cpl_pop is ', join_sum
         endif
      endif


! ---- send/recv messages among components ----
! ---- Note the use of MPH_global_id() function.

!--- Ocean proc 3 recv a message from coupler proc 0

      if (myProc_global == MPH_global_id("ocean",3)) then
         write(*,*) 'I am pop 3, recv from cpl 0'
         call MPI_RECV (c2o_yes, 300, MPI_CHARACTER,
     &                  MPH_global_id("coupler", 0), 3000,
     &                  MPI_COMM_World, istatus, ierr)
         write(*,*)'I am pop 3, expect c2o=abcdefg'
         write(*,*)'pop 3 gets c2o(1)=', c2o_yes(1)
      endif

!--- atmosphere proc 1 send a message to coupler proc 3

      a2c= 100
      if (myProc_global == MPH_global_id("atmosphere", 1)) then
         write(*,*)'I am ccm 1, send to cpl 3'
         call MPI_SEND (a2c, 100, MPI_INTEGER,
     &                  MPH_global_id("coupler", 3),
     &                  1000, MPI_COMM_World, ierr)
         write(*,*)'ccm 1 sent to cpl 3 successfully'
      endif

!--- coupler proc 0 recv a message from atmosphere proc 1,
!--- coupler proc 3 send a message to ocean proc 5

      c2o = 'abcdefg'

      if (myProc_global == MPH_global_id("coupler", 0)) then
         write(*,*)'I am cpl 0, send to pop 3'
         call MPI_SEND (c2o, 300, MPI_CHARACTER,
     &                  MPH_global_id ("ocean", 3), 3000,
     &                  MPI_COMM_World,ierr)
         write(*,*)'cpl 0 sent to pop 3 successfully'
      endif

      if (myProc_global == MPH_global_id("coupler", 3)) then
         write(*,*)'I am cpl 3, recv from ccm 1'
         call MPI_RECV (a2c_yes, 100, MPI_INTEGER,
     &                  MPH_global_id ("atmosphere", 1), 1000,
     &                  MPI_COMM_World, istatus, ierr)
         write(*,*)'I am cpl 3, expect a2c(1)=100'
         write(*,*)'cpl 3 gets a2c(1)=', a2c_yes(1)
      endif

      write(*,*)'=============================================='
      call MPI_FINALIZE (ierr)

      end program