program reduction
        include 'mpif.h'
       integer numtasks, rank, count, source, ierr 
       real*4 sendbuf, recvbuf 
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)
       sendbuf= rank
       count=1
       source=0
       call MPI_ALLREDUCE(sendbuf, recvbuf,count,MPI_REAL, 
     &  MPI_SUM, MPI_COMM_WORLD, ierr) 
       print *, 'rank= ',rank,' Results: ',recvbuf
       call MPI_FINALIZE(ierr) 
       end