The function may be called by the names: s14ahc, nag_specfun_gamma_log_scaled_real or nag_scaled_log_gamma.
s14ahc calculates an approximate value for , where . This is a variant of the function (see also s14abc), which avoids rounding problems for very large arguments by computing with the Stirling approximation factored out.
For , ;
and for , , where is a suitable Remez approximation.
For , the value is undefined; s14ahc returns zero and exits with NE_REAL_ARG_LE.
The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).
6Error Indicators and Warnings
Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 7.5 in the Introduction to the NAG Library CL Interface for further information.
Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.
On entry, .
s14ahc has been designed to produce full relative accuracy for all input arguments. Empirical results obtained by comparing with multiprecision software confirm this.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
s14ahc is not threaded in any implementation.
This example reads values of the argument from a file, evaluates the function at each value of and prints the results.