subroutine sort (irpa, ndif)
c
c-----------------------------------------------------------------------
c
c     Routine puts the ndif values in irpa(ndif) into ascending
c     (positive) order
c
c-----------------------------------------------------------------------
c
      integer*4 irpa(ndif), ndif
c
c-----------------------------------------------------------------------
c-----------------------------------------------------------------------
c
      if (ndif .le. 1) return
c
c-----------------------------------------------------------------------
c     ***   perform a bubble sort, ic flags   ***
c     *** whether a swap has been made or not ***
c-----------------------------------------------------------------------
c
      do ik = 1, ndif
         ic = 0
c
c-----------------------------------------------------------------------
c        *** scan though all the values, compare adjacent ones ***
c-----------------------------------------------------------------------
c
         do  i = 2, ndif
            if (irpa(i-1) .gt. irpa(i)) then
c
c-----------------------------------------------------------------------
c           *** first one large, so swap ***
c-----------------------------------------------------------------------
c
               ic = 1
               itemp = irpa(i)
               irpa(i) = irpa(i-1)
               irpa(i-1) = itemp
            end if
         end do
c
c-----------------------------------------------------------------------
c        *** if no swaps made, we can return prematurely ***
c-----------------------------------------------------------------------
c
         if (ic .eq. 0) return
      end do
c
c-----------------------------------------------------------------------
c-----------------------------------------------------------------------
c
      return
      end