program gather
        include 'mpif.h'
        integer SIZE 
        parameter(SIZE=4) 
       integer numtasks, rank, sendcount, recvcount, source, ierr 
       real*4 sendbuf(SIZE), recvbuf(SIZE,SIZE) 
C Fortran stores this array in column major order, so the 
C scatter will actually scatter columns, not rows. 
       call MPI_INIT(ierr) 
       call MPI_COMM_RANK(MPI_COMM_WORLD, rank, ierr) 
       call MPI_COMM_SIZE(MPI_COMM_WORLD, numtasks, ierr)
       Do i=1,size
       Sendbuf(i)=rank*size+I
       enddo 
       if (numtasks .eq. SIZE) then 
       source = 1 
       sendcount = SIZE 
       recvcount = SIZE
       call MPI_GATHER(sendbuf, sendcount, MPI_REAL, recvbuf, 
     & recvcount, MPI_REAL, source, MPI_COMM_WORLD, ierr) 
       If(rank.eq.1)then
       print *, 'rank= ',rank,' Results: ',recvbuf
       endif 
       else 
        print *, 'Must specify',SIZE,' processors. Terminating.' 
       endif 
       call MPI_FINALIZE(ierr) 
       end