NAG Library Routine Document

G01ZUF

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 Parameters

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 – INTEGERInput: On entry: if $MODE = 0$ , then 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) arrayCommunication Array: On exit: this parameter should be passed unchanged to G01EUF or G01MUF.
7: IFAIL – INTEGERInput/Output: On entry: IFAIL must be set to $0$ , $- 1 or 1$ . If you are unfamiliar with this parameter you should refer to Section 3.3 in the Essential Introduction for details.
For environments where it might be inappropriate to halt program execution when an error is detected, the value $- 1 or 1$ is recommended. If the output of error messages is undesirable, then the value $1$ is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is $0$ . 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,	$RKAPPA < 0.01$ ,
or	$RKAPPA > 10.0$ ,
or	$BETA2 < 0.0$ ,
or	$BETA2 > 1.0$ .

$IFAIL = 2$: 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.