module periodicity
       
        real*8, allocatable :: rcount(:)
        end module


       subroutine setper (nshg)
       
       use periodicity

       allocate (rcount(nshg))
       
       return
       end

       subroutine clearper
         use periodicity
         if( allocated(rcount) ) then
           deallocate(rcount)
         endif
       end

       subroutine perprep (iBC, iper,nshg)
       
       use periodicity

       dimension iBC(nshg),
     &           iper(nshg)       
  
c
c..... calculate the inverse of the number of slaves + 1
c
       one=1.00000000000
       rcount=one
       do j = 1,nshg
          if (btest(iBC(j),10)) then
             i = iper(j)
             rcount(i) = rcount(i) + one
          endif
       enddo
       do k=1,nshg
          if(rcount(k).ne.one) then
             rcount(k)=one/rcount(k)
          endif
       enddo
      
c
c.... return
c
       return
       end