program main
      integer nproc, my_rank, ierr
      call init(nproc,my_rank)
      if (my_rank.EQ.0) then
        call master(nproc)
      else
        call slave(my_rank)
      endif
      call MPI_Finalize(ierr)
      stop
      end
c
      subroutine init(nproc,my_rank)
      include "mpif.h"
      integer nproc,my_rank,ierr
      character*30 nodename
      integer nchar
      call MPI_init(ierr)
      call MPI_Comm_rank(MPI_COMM_WORLD,my_rank,ierr)
      call MPI_Comm_size(MPI_COMM_WORLD,nproc,ierr)
      call MPI_Get_processor_name(nodename,nchar,ierr)
      write(*,*) 'my_rank=',my_rank,'processor=',nodename
      return
      end
c
      subroutine master(nproc)
      include "mpif.h"
      integer nproc,ierr,idest,itag,status(MPI_STATUS_SIZE)
      real*8 a, b, c
      nproc1=nproc-1
      do i=1,nproc1
        a=dfloat(i)
        b=dfloat(i*i)
        idest=i
        itag=10
        call MPI_Send(a,1,MPI_DOUBLE_PRECISION,idest,itag,
     &                MPI_COMM_WORLD,ierr)
        itag=20
        call MPI_Send(b,1,MPI_DOUBLE_PRECISION,idest,itag,
     &                MPI_COMM_WORLD,ierr)
      enddo
      do i=1,nproc-1
        isrc=i
        itag=110
        call MPI_RECV(a,1,MPI_DOUBLE_PRECISION,isrc,
     &       itag,MPI_COMM_WORLD,status,ierr)
        itag=120
        call MPI_RECV(b,1,MPI_DOUBLE_PRECISION,isrc,
     &       itag,MPI_COMM_WORLD,status,ierr)
        itag=130
        call MPI_RECV(c,1,MPI_DOUBLE_PRECISION,isrc,
     &       itag,MPI_COMM_WORLD,status,ierr)
        write(*,*) 'slave #',isrc,'a=',a,'b=',b,'c=',c
      enddo
      return
      end
c
      subroutine slave(my_rank)
      include "mpif.h"
      integer status(MPI_STATUS_SIZE)
      real*8 a, b, c
      itag=10
      isrc=0
      call MPI_RECV(a,1,MPI_DOUBLE_PRECISION,isrc,
     &     itag,MPI_COMM_WORLD,status,ierr)
      itag=20
      call MPI_RECV(b,1,MPI_DOUBLE_PRECISION,isrc,
     &     itag,MPI_COMM_WORLD,status,ierr)
      c=a+b
      itag=110
      idest=0
      call MPI_Send(a,1,MPI_DOUBLE_PRECISION,idest,itag,
     &     MPI_COMM_WORLD,ierr)
      itag=120
      call MPI_Send(b,1,MPI_DOUBLE_PRECISION,idest,itag,
     &     MPI_COMM_WORLD,ierr)
      itag=130
      call MPI_Send(c,1,MPI_DOUBLE_PRECISION,idest,itag,
     &     MPI_COMM_WORLD,ierr)
      return
      end