Fabian writes: > I just thought that if you set s to "1.0 / gsl_complex_abs2 (a)" this will underflow if |a| > sqrt(DBL_MAX) See volume 1 of the book "Numerical Computation" by C.Ueberhuber for a good discussion of IEEE arithmetic. -- Brian Gough Network Theory Ltd, Commercial support for GSL --- http://www.network-theory.co.uk/gsl/