The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).
6Error Indicators and Warnings
NE_ALLOC_FAIL
Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.
NE_INTERNAL_ERROR
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.
NE_NO_LICENCE
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.
NE_REAL_ARG_GT
On entry, . Constraint: . is too large and the function returns the approximate value of at the nearest valid argument.
7Accuracy
Let and be the relative errors in the argument and result respectively.
If is somewhat larger than the machine precision (i.e., if is due to data errors etc.), then and are approximately related by:
Figure 1 shows the behaviour of the error amplification factor
Figure 1
However, if is of the same order as machine precision, then rounding errors could make slightly larger than the above relation predicts.
For small , and there is no amplification of errors.
For large , and we have strong amplification of errors. However, the function must fail for quite moderate values of because would overflow; hence in practice the loss of accuracy for large is not excessive. Note that for large , the errors will be dominated by those of the standard math library function exp.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
s18afc is not threaded in any implementation.
9Further Comments
None.
10Example
This example reads values of the argument from a file, evaluates the function at each value of and prints the results.
