Could you tell me a fast and accurate method to calcuate BesselK(mu,z), BesselI(mu,z), where mu is real number?
There are several ways to represent the Bessel functions and none of them are easy to do mathematically or closed-form. However, this paper seems to be a recent approach to evaluating them efficiently:
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.120.6055
It seems to be a better way than the old-school method from the 1950s:
http://www.ams.org/journals/mcom/1959-13-066/S0025-5718-1959-0105794-5/S0025-5718-1959-0105794-5.pdf