subroutine algams (x, algam, sgngam)
  c july 1977 edition.  w. fullerton, c3, los alamos scientific lab.
  c
  c evaluate log abs (gamma(x)) and return the sign of gamma(x) in sgngam.
  c sgngam is either +1.0 or -1.0.
  c
        external  alngam
  c
        algam = alngam(x)
        sgngam = 1.0
        if (x.gt.0.0) return
  c
        int = amod (-aint(x), 2.0) + 0.1
        if (int.eq.0) sgngam = -1.0
  c
        return
        end