!Homework 15
!Programmer: Chad Brewbaker
!Email address: crb002@iastate.edu
!Date: April 22, 2004
!Machine used: hpc-class.iastate.edu (Intel Xenon/Myrinet cluster)
!Compiler options used:
implicit none
include "mpif.h"
integer,parameter :: n=5,dp=mpi_double_precision, comm=mpi_comm_world
integer :: p, rank, i, status(mpi_status_size)
integer :: ierror,newtype,blocklens(n),disp(n)
double precision :: A(n,n), B(n,n)

call mpi_init(ierror)
call mpi_comm_size(comm, p, ierror)
call mpi_comm_rank(comm, rank, ierror)


if (rank == 0) then
   print *, '     '
   print *, ' p = ', p, ' and n = ', n
   call random_number(A)
   print *, 'A= ', A(1:n,1:n)
endif

!!Get a lower triangular nxn matrix from the diagonal down.

do i=1,n
   !Why does this do row major??
   ! blocklens(i)=n-i+1
   !disp(i)=(n*(i-1))+i-1
   blocklens(i)=i
   disp(i)=(n*(i-1))
enddo
call MPI_Type_indexed(n,blocklens,disp,dp,newtype,ierror)
call  MPI_Type_commit(newtype,ierror)

if (rank==0) then
   call MPI_Send(A, 1, newtype, 1, 1, comm, ierror)
endif

if(rank==1) then
   B=0.d0
   call MPI_Recv(B, 1, newtype, 0, 1,comm, status, ierror)
   print *, 'B= ', B(1:n,1:n)
endif
 
call MPI_Type_free(newtype,ierror)
call mpi_finalize(ierror)
endprogram
!!$ B=   0.773267129885890        0.00000000000000D+000   0.00000000000000D+000
!!$  p =            2  and n =            5
!!$ A=   0.773267129885890       0.823251234348674       0.148120620308437     
!!$  0.656714907139731       0.842055630151761       0.628580122014474     
!!$  0.330478665894452       0.768815101108699       0.681063573564108     
!!$  0.104431626409966       0.285990417481750       0.809037499810276     
!!$  0.743652890654999       0.725900004139059        7.35362302760166D-002
!!$  0.736122963470632       0.821746784010800        3.96838647115694D-002
!!$  0.621942684745769        6.36071097359756D-002  0.356516153094329     
!!$  0.817688434831933       0.441321639580342       0.527589249423030     
!!$  0.873512638478219     
!!$   0.00000000000000D+000   0.00000000000000D+000  0.628580122014474     
!!$  0.330478665894452        0.00000000000000D+000   0.00000000000000D+000
!!$   0.00000000000000D+000  0.285990417481750       0.809037499810276     
!!$  0.743652890654999        0.00000000000000D+000   0.00000000000000D+000
!!$  0.736122963470632       0.821746784010800        3.96838647115694D-002
!!$  0.621942684745769        0.00000000000000D+000  0.356516153094329     
!!$  0.817688434831933       0.441321639580342       0.527589249423030