!Homework 8 using collectives on 4
!Programmer: Chad Brewbaker
!Email address: crb002@iastate.edu
!Date: Febuary 16, 2004
!Machine used: hpc-class.iastate.edu (Intel Xenon cluster)
!Compiler options used:


program
implicit none
integer, parameter :: n=3
real*8,dimension(:,:),allocatable::A
real*8::B(n)
include "mpif.h"
integer::i,j,k,ierror,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)

call random_number(B)
B(1:n)=B(1:n)+rank
print *,  'On processor',rank,'B=',B

if(rank==0)then
   allocate(A(n,0:p-1))
endif
call MPI_Gather(B,n,MPI_REAL8,A,n,MPI_REAL8,0,MPI_COMM_WORLD,ierror)

if(rank==0)then
   do i=0,p-1
      print *,'Column',i,' of A=',A(1:n,i)
   enddo
   deallocate(A)
endif

call MPI_Finalize(ierror)
end program

!!$vincent% mpirun -np 4 hw8.4.exe
!!$ On processor           2 B=   2.77326712988589        2.82325123434867     
!!$   2.14812062030844     
!!$ On processor           3 B=   3.77326712988589        3.82325123434867     
!!$   3.14812062030844     
!!$ On processor           0 B=  0.773267129885890       0.823251234348674     
!!$ On processor           1 B=   1.77326712988589        1.82325123434867     
!!$  0.148120620308437     
!!$ Column           0  of A=  0.773267129885890       0.823251234348674     
!!$  0.148120620308437     
!!$ Column           1  of A=   1.77326712988589        1.82325123434867     
!!$   1.14812062030844     
!!$ Column           2  of A=   2.77326712988589        2.82325123434867     
!!$   2.14812062030844     
!!$ Column           3  of A=   3.77326712988589        3.82325123434867     
!!$   3.14812062030844     
!!$   1.14812062030844     
!!$vincent%