I only need it to work for real arguments. But if that were an issue I could stick with Lanczos. Any given set of Lanczos parameters work equally well on the entire half-plane Real[z]>0, and with the same guaranteed error bound. This article describes it really well: http://www.haoli.org/nr/bookcpdf/c6-1.pdf which is from: William H. Press et al., Numerical recipes in C: the art of scientific computing (2nd edition). Cambridge University Press, (1992) ISBN 0521431085. On Mon, Jan 9, 2012 at 12:06, Warren Smith <warren.wds@gmail.com> wrote:
Do you want it to work for complex or only for real argument?
I've been looking for a numeric Gamma method that gives 34 digits of precision suitable for quad-precision floating-point [2] although I would settle for 31 digits suitable for "double-double".
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