module mpi
          include 'mpif.h'
       end module mpi


       module cpuids
          integer::myid,totps, ierr
       end module cpuids


       program example02
       use mpi
       use cpuids
       call mpiinit
       call demo02
       call mpi_finalize(ierr)
       stop
       end


       subroutine mpiinit
       use mpi
       use cpuids
       call mpi_init( ierr )
       call mpi_comm_rank(
     &          mpi_comm_world,myid,ierr)
       call mpi_comm_size(
     &          mpi_comm_world,totps,ierr)
       return
       end


       subroutine demo02
       use mpi
       use cpuids
       integer:: m, i
       real*8 :: s, mys
       if(myid.eq.0) then
           write(*,*)'how many terms?'
           read(*,*) m
       end if
       call mpi_bcast(m,1,
     &          mpi_integer,0,
     &          mpi_comm_world,ierr)
       mys=0.0d0
       do i=myid,m,totps
          mys=mys+dsqrt(dfloat(i))
       end do
       write(*,*)'rank:', myid,  
     &           'mys=',mys,  ' m:',m       
       s=0.0d0
       call mpi_reduce(mys,s,1,
     &          mpi_real8,mpi_sum,0, 
     &          mpi_comm_world,ierr)
       if(myid.eq.0) then
           write(*,*)'total sum:  ', s
       end if
       return
       end