A remark on Algorithm 644
Donald E. Amos · ACM Transactions on Mathematical Software · 1995
Algorithm 644 computes all major Bessel functions of a complex argument and of nonnegative order. Single-precision routine CBESY and double-precision routine ZBESY are modified to reduce the computation time for the Y Bessel function by approximately 25% over a wide range of arguments and orders. Quick check (driver) programs that exercise the package are also modified to make tests more meaningful over larger regions of the complex plane.