!Homework 1

!Febuary 2004
!Machine hpc-class.iastate.edu
!Programmer: Chad Brewbaker


program
implicit none
integer, parameter :: n=4
integer::i,ierror
real*8,dimension(n)::A,B,C,D
include "mpif.h"
integer::p,rank,status(mpi_status_size)
call mpi_init(ierror)
call mpi_comm_size(mpi_comm_world,p,ierror)
call mpi_comm_rank(mpi_comm_world,rank,ierror)

if(rank==0)then
   do i=1,n
      A(i)=float(i)
   enddo
   call MPI_Send(A(1),n,MPI_REAL8,1,1,MPI_COMM_WORLD,ierror)
   call MPI_Recv(D(1),n,MPI_REAL8,MPI_ANY_SOURCE, 1, MPI_COMM_WORLD,status,ierror)
   print *,'D='
   do i=1,n
      print *,D(i)
   enddo
   print *,'on processor of rank',rank
endif

if(rank==1)then
   call MPI_Recv(A(1),n,MPI_REAL8,MPI_ANY_SOURCE,1,MPI_COMM_WORLD,status,ierror)
   do i=1,n
      B(i)=A(i)+1
   enddo
   call MPI_Send(B(1),n,MPI_REAL8,2,1,MPI_COMM_WORLD,ierror)
endif

if(rank==2)then
   call MPI_Recv(B(1),n,MPI_REAL8,MPI_ANY_SOURCE,1,MPI_COMM_WORLD,status,ierror)
   do i=1,n
      C(i)=B(i)+1
   enddo
   call MPI_Send(C(1),n,MPI_REAL8,0,1,MPI_COMM_WORLD,ierror)
endif

!!$if(rank==3)then
!!$   call MPI_Recv(C(1),n,MPI_REAL8,MPI_ANY_SOURCE,1,MPI_COMM_WORLD,status,ierror)
!!$   do i=1,n
!!$      D(i)=C(i)+1
!!$   enddo
!!$   call MPI_Send(D(1),n,MPI_REAL8,0,1,MPI_COMM_WORLD,ierror)
!!$endif

call MPI_Finalize(ierror)
end program

!!$RESULTS
!!$
!!$vincent% mpirun -np 4 ./hw1.exe
!!$ D=
!!$   3.00000000000000
!!$   4.00000000000000
!!$   5.00000000000000
!!$   6.00000000000000
!!$ on processor of rank           0
!!$vincent%