NAG Library Routine Document
g01rtf returns the value of the derivative of the Landau density function, via the routine name.
|Real (Kind=nag_wp)||:: ||g01rtf|
|Real (Kind=nag_wp), Intent (In)||:: ||x|C Header Interface
g01rtf_ (const double *x)|
evaluates an approximation to the derivative
of the Landau density function given by
is described in g01mtf
, using piecewise approximation by rational functions. Further details can be found in Kölbig and Schorr (1984)
To obtain the value of
can be used.
Kölbig K S and Schorr B (1984) A program package for the Landau distribution Comp. Phys. Comm. 31 97–111
- 1: – Real (Kind=nag_wp)Input
On entry: the argument of the function.
Error Indicators and Warnings
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.
Parallelism and Performance
g01rtf is not threaded in any implementation.
This example evaluates at , and prints the results.
Program Text (g01rtfe.f90)
Program Data (g01rtfe.d)
Program Results (g01rtfe.r)