function cabs (z)
c december 1978 version.  w. fullerton, c3, los alamos scientific lab.
      complex z
      external r1mach, sqrt
      data sqeps, big, xmax / 3*0.0/
c
      if (sqeps.ne.0.0) go to 10
      sqeps = sqrt (r1mach(4))
      xmax = r1mach(2)
      big = xmax/1.415
c
 10   x = abs (real (z))
      y = abs (aimag (z))
      r1 = amin1 (x, y)
      r2 = amax1 (x, y)
c
      if (r1.gt.big) go to 20
      cabs = r2
      if (r1.gt.r2*sqeps) cabs = r2*sqrt(1.0+(r1/r2)**2)
      return
c
 20   r1 = sqrt (1.0+(r1/r2)**2)
      if (r2.gt.xmax/r1) call seteru (
     1  46hcabs    cabs(z) overflows because z is too big, 46, 1, 2)
      cabs = r2*r1
      return
c
      end

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