subroutine d9upak (x, y, n)
  c august 1980 portable edition.  w. fullerton, los alamos scientific lab
  c
  c unpack floating point number x so that x = y * 2.0**n, where
  c 0.5 .le. abs(y) .lt. 1.0 .
  c
        double precision x, y, absx
  c
        absx = dabs(x)
        n = 0
        y = 0.0d0
        if (x.eq.0.0d0) return
  c
   10   if (absx.ge.0.5d0) go to 20
        n = n - 1
        absx = absx*2.0d0
        go to 10
  c
   20   if (absx.lt.1.0d0) go to 30
        n = n + 1
        absx = absx*0.5d0
        go to 20
  c
   30   y = dsign (absx, x)
        return
  c
        end