nag_bessel_k_nu (s18efc) evaluates an approximation to the modified Bessel function of the second kind
, where the order
or
and
is real and positive. For negative orders the formula
is used.
All constants in the underlying function are specified to approximately 18 digits of precision. If denotes the number of digits of precision in the floating-point arithmetic being used, then clearly the maximum number of correct digits in the results obtained is limited by . Because of errors in argument reduction when computing elementary functions inside the underlying function, the actual number of correct digits is limited, in general, by , where represents the number of digits lost due to the argument reduction. Thus the larger the value of , the less the precision in the result.
Not applicable.
None.