program nasa_ex2
!-- Template for any mpi program
! Starting from template.f, write a program that given a 
!common value of x (e.g. x=5 in all processes), computes:
!     * y=x2 in process 0
!     * y=x3 in process 1
!     * y=x4 in process 2 
! and writes a statement from each process that identifies the 
!process and reports the values of x and y from that process.

!--Include the mpi header file       
  use mpi       
  implicit none    ! highly recommended. It will make
                   ! debugging infinitely easier.
!--Declare all variables and arrays.
  integer :: ierr,myid,numprocs,itag
  integer :: irc, comm
  real    :: x,y,z
!--Initialize MPI
  call MPI_INIT( ierr )      ! --> Required statement
   
!--Who am I? --- get my rank=myid
  call MPI_COMM_RANK( MPI_COMM_WORLD, myid, ierr )
  comm = MPI_COMM_WORLD

call system( 'sleep 5' )
!--How many processes in the global group?
  call MPI_COMM_SIZE( MPI_COMM_WORLD, numprocs, ierr )

!set the value of x on root processor, 
  if (myid == 0) x=5 
  
!then broadcast to all procs   
    call MPI_BCAST(x,1,mpi_real, 0,comm,ierr)
  
! compute based which proc I am
  if (myid == 0) then
    y=x**2
!    call MPI_BCAST(x,1,mpi_real, 0,comm,ierr)
  else if (myid == 1) then
!    call MPI_BCAST(z,1,mpi_real, 0,comm,ierr)
    y=x**3
  else if (myid == 2) then
!    call MPI_BCAST(z,1,mpi_real, 0,comm,ierr)
    y=x**4
  end if

!-- print y
  write(*,*)'On process ',myid,' x=',x,',  y=',y,'  z=',z

!--Finalize MPI
  call MPI_FINALIZE(irc)     ! ---> Required statement
   
  stop
end