program mpi_type_vector_test

! Declare variables
use mpi
implicit none
integer :: n_proc, n_rank, ierr, i,j 
integer :: myvector, myvector_size
integer, parameter :: n=5, nb=2
integer(kind=MPI_ADDRESS_KIND) myvector_extent, myvector_lb
real :: a(n,n)
integer :: mystatus(MPI_STATUS_SIZE)

! Start MPI
call MPI_Init(ierr)
call MPI_Comm_size(MPI_COMM_WORLD,n_proc,ierr)
call MPI_Comm_rank(MPI_COMM_WORLD,n_rank,ierr)

! Check the number of processes is 2
if(n_proc /= 2) then
  if(n_rank == 0) print*,'Test program has to work only with two MPI processes'
  call MPI_Finalize(ierr)
  STOP
endif

! Initialize matrix
if(n_rank == 0) a=0
if(n_rank == 1) a=1

! Define vector, extract and print size and extent:
! - vector should include the values of the first two rows of the matrix
! - the function MPI_Type_vector may be used to define the new data type 
! - 'myvector' would be the new handle
	---

! - which functions would you use to get 'myvector_size', 'myvector_lb'
! - and 'myvector_extent' ?
	---

print*,'MPI myvector size,lb,extent: ',myvector_size,myvector_lb,myvector_extent

! Print matrix a for rank=1
if (n_rank == 1) then
  print*,'Matrix A before communications:'
  do i=1,n
     do j=1,n
        write(*,'(F10.2,1X)',advance='no') a(i,j)
     enddo
     write(*,*) 
  enddo
endif

! Communicate
if(n_rank == 0) then
   call MPI_Send(a,1,myvector,1,100,MPI_COMM_WORLD, ierr)
endif
if(n_rank == 1) then
   call MPI_Recv(a,1,myvector,0,100,MPI_COMM_WORLD, mystatus, ierr)
endif

! Print matrix a for rank=1
if(n_rank == 1) then
  print*,'Matrix A after communications:'
  do i=1,n
     do j=1,n
        write(*,'(F10.2,1X)',advance='no') a(i,j)
     enddo
     write(*,*) 
  enddo
endif

call MPI_Type_free(myvector, ierr)

! Finalize MPI
call MPI_Finalize(ierr)

end program mpi_type_vector_test