Note: before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.
G01ETF evaluates an approximation to the Landau distribution function given by
where is described in G01MTF, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984).
4 References
Kölbig K S and Schorr B (1984) A program package for the Landau distribution Comp. Phys. Comm.31 97–111
5 Parameters
1: X – REAL (KIND=nag_wp)Input
On entry: the argument of the function.
6 Error Indicators and Warnings
There are no failure exits from this routine.
7 Accuracy
At least significant digits are usually correct, but occasionally only . Such accuracy is normally considered to be adequate for applications in experimental physics.
Because of the asymptotic behaviour of , which is of the order of , underflow may occur on some machines when is moderately large and negative.
8 Further Comments
None.
9 Example
This example evaluates at , and prints the results.