Integer, Intent (In)	::	mode
Integer, Intent (Inout)	::	ifail
Real (Kind=nag_wp), Intent (In)	::	rkappa, beta2
Real (Kind=nag_wp), Intent (Out)	::	xl, xu, rcomm(322)

C Header Interface

#include <nag.h>

void	g01zuf_ (const double rkappa, const double beta2, const Integer mode, double xl, double xu, double rcomm[], Integer ifail)

The routine may be called by the names g01zuf or nagf_stat_init_vavilov.

3 Description

g01zuf initializes the array rcomm for use by g01euf or g01muf in the evaluation of the Vavilov functions

ϕ_{V} (λ; κ, β^{2})

and

Φ_{V} (λ; κ, β^{2})

respectively.

Multiple calls to g01euf or g01muf can be made following a single call to g01zuf, provided that rkappa or beta2 do not change, and that either all calls are to g01euf or all calls are to g01muf. If you wish to call both g01euf and g01muf, then you will need to initialize both separately.

4 References

Schorr B (1974) Programs for the Landau and the Vavilov distributions and the corresponding random numbers Comp. Phys. Comm. 7 215–224

5 Arguments

1: $rkappa$ – Real (Kind=nag_wp) Input: On entry: the argument $κ$ of the function.

Constraint: $0.01 \leq rkappa \leq 10.0$ .
2: $beta2$ – Real (Kind=nag_wp) Input: On entry: the argument $β^{2}$ of the function.

Constraint: $0.0 \leq beta2 \leq 1.0$ .
3: $mode$ – Integer Input: On entry: if $mode = 0$ , g01muf is to be called after the call to g01zuf. Otherwise, g01euf is to be called.
4: $xl$ – Real (Kind=nag_wp) Output: On exit: $x_{l}$ , a threshold value below which $ϕ_{V} (λ; κ, β^{2})$ will be set to zero by g01muf and $Φ_{V} (λ; κ, β^{2})$ will be set to zero by g01euf if $λ < x_{l}$ .
5: $xu$ – Real (Kind=nag_wp) Output: On exit: $x_{u}$ , a threshold value above which $ϕ_{V} (λ; κ, β^{2})$ will be set to zero by g01muf and $Φ_{V} (λ; κ, β^{2})$ will be set to unity by g01euf if $λ > x_{u}$ .
6: $rcomm (322)$ – Real (Kind=nag_wp) array Communication Array: On exit: this argument should be passed unchanged to g01euf or g01muf.
7: $ifail$ – Integer Input/Output: On entry: ifail must be set to $0$ , $−1$ or $1$ to set behaviour on detection of an error; these values have no effect when no error is detected.
A value of $0$ causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of $−1$ means that an error message is printed while a value of $1$ means that it is not.

If halting is not appropriate, the value $−1$ or $1$ is recommended. If message printing is undesirable, then the value $1$ is recommended. Otherwise, the value $0$ is recommended. When the value $- 1$ or $1$ is used it is essential to test the value of ifail on exit.

On exit: $ifail = 0$ unless the routine detects an error or a warning has been flagged (see Section 6).

6 Error Indicators and Warnings

If on entry

ifail = 0

−1

, explanatory error messages are output on the current error message unit (as defined by x04aaf).

Errors or warnings detected by the routine:

$ifail = 1$: On entry, $beta2 = ⟨ value ⟩$ .
Constraint: $beta2 \leq 1.0$ .

On entry, $beta2 = ⟨ value ⟩$ .
Constraint: $beta2 \geq 0.0$ .

On entry, $rkappa = ⟨ value ⟩$ .
Constraint: $rkappa \leq 10.0$ .

On entry, $rkappa = ⟨ value ⟩$ .
Constraint: $rkappa \geq 0.01$ .

$ifail = 2$: The initialization has been abandoned due to an internal error. This error exit is unlikely to occur, but if it does change the values of rkappa and/or beta2 and rerun g01zuf.

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.