subroutine slave(my_rank)
      include "mpif.h"
      parameter (l=500)
      integer my_rank,ne,icn(l,3),icn1(l),icn2(l),icn3(l)
      integer status(MPI_STATUS_SIZE)
      real*8 x(l),y(l),z(l)
      real*8 h1(l),g1(l),xn(l,3),ar
      real*8 xc1,yc1,zc1
      integer  itag1,itag2,ipos,idest
      parameter (BUFSIZE=50000)
      character buf(50000)
      ik=100
      do while(ik.ne.-1) 
         l3=l*3
         ipos=0
         isrc=0
         itag1=10
         call MPI_Recv(buf,BUFSIZE,MPI_PACKED,isrc,itag1,
     1        MPI_COMM_WORLD,status,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,nproc,1,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,ne,1,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,np,1,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,icn1,ne,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,icn2,ne,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,icn3,ne,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,x,np,MPI_DOUBLE_PRECISION,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,y,np,MPI_DOUBLE_PRECISION,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,z,np,MPI_DOUBLE_PRECISION,
     1        MPI_COMM_WORLD,ierr)
         call MPI_Unpack(buf,BUFSIZE,ipos,n,1,MPI_INTEGER,
     1        MPI_COMM_WORLD,ierr)
         ik=n 
         if(ik.ne.-1) then
            write(*,*) 'my_rank=',my_rank,'  ik=',ik
            do i=1,ne
               icn(i,1)=icn1(i)
               icn(i,2)=icn2(i)
               icn(i,3)=icn3(i)
            enddo
            call potn(ik,ne,icn,x,y,z,xc1,yc1,zc1,xn,h1,g1,l,ar,np)
            l3=l*3
            ipos=0
            iflag2=20
            idest=0
            call MPI_Pack(xc1,1,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(yc1,1,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(zc1,1,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(xn,l3,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(ar,1,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(ne,1,MPI_INTEGER,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(h1,ne,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(g1,ne,MPI_DOUBLE_PRECISION,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(my_rank,1,MPI_INTEGER,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Pack(ik,1,MPI_INTEGER,buf,BUFSIZE,ipos,
     *           MPI_COMM_WORLD,ierr)
            call MPI_Send(buf,ipos,MPI_PACKED,idest,itag2,
     *           MPI_COMM_WORLD,ierr)
         endif
      enddo
      return
      end