message-chain/fortran/skeleton.F90

+program basic
+  use mpi
+  use iso_fortran_env, only : REAL64
+
+  implicit none
+  integer, parameter :: size = 10000000
+  integer :: rc, myid, ntasks
+  integer :: message(size)
+  integer :: receiveBuffer(size)
+  integer :: status(MPI_STATUS_SIZE)
+
+  real(REAL64) :: t0, t1
+
+  call mpi_init(rc)
+  call mpi_comm_rank(MPI_COMM_WORLD, myid, rc)
+  call mpi_comm_size(MPI_COMM_WORLD, ntasks, rc)
+
+  message = myid
+
+  ! Start measuring the time spent in communication
+  call mpi_barrier(mpi_comm_world, rc)
+  t0 = mpi_wtime()
+
+  ! TODO: Send and receive as defined in the assignment
+  if ( myid < ntasks-1 ) then
+
+     write(*,'(A10,I3,A20,I8,A,I3,A,I3)') 'Sender: ', myid, &
+          ' Sent elements: ',size, &
+          '. Tag: ', myid+1, '. Receiver: ', myid+1
+  end if
+
+  if ( myid > 0 ) then
+
+     write(*,'(A10,I3,A,I3)') 'Receiver: ', myid, &
+          ' First element: ', receiveBuffer(1)
+  end if
+
+  ! Finalize measuring the time and print it out
+  t1 = mpi_wtime()
+  call mpi_barrier(mpi_comm_world, rc)
+  call flush(6)
+
+  if (myid == 0) then
+      write(*,*)
+      write(*,*) 'Timings:'
+      write(*, '(A20, I3, A, F6.3)') 'Time elapsed in rank', myid, ':', t1-t0
+  endif
+  call mpi_barrier(mpi_comm_world, rc)
+  call flush(6)
+  if (myid == ntasks - 1) then
+      write(*, '(A20, I3, A, F6.3)') 'Time elapsed in rank', myid, ':', t1-t0
+  endif
+
+  call mpi_finalize(rc)
+
+end program basic