# NAG FL Interfacee04znf (handle_​opt_​get)

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## 1Purpose

e04znf is an option getting routine for all solvers from the NAG optimization modelling suite. It is used to query the value of optional parameters.

## 2Specification

Fortran Interface
 Subroutine e04znf (
 Integer, Intent (Inout) :: ifail Integer, Intent (Out) :: ivalue, optype Real (Kind=nag_wp), Intent (Out) :: rvalue Character (*), Intent (In) :: optstr Character (*), Intent (Out) :: cvalue Type (c_ptr), Intent (In) :: handle
#include <nag.h>
 void e04znf_ (void **handle, const char *optstr, Integer *ivalue, double *rvalue, char *cvalue, Integer *optype, Integer *ifail, const Charlen length_optstr, const Charlen length_cvalue)
The routine may be called by the names e04znf or nagf_opt_handle_opt_get.

## 3Description

e04znf is used to query the current values of optional parameters. It can be especially useful to retrieve the optional parameters left for automatic choice by the solver.
This routine will normally return either an integer, real or character value dependent upon the type associated with the optional parameter being queried. This is indicated by the returned value of optype.
Information relating to available option names is given in the documentation of the particular solver. See also Section 3.1 in the E04 Chapter Introduction for more details about the NAG optimization modelling suite.

None.

## 5Arguments

1: $\mathbf{handle}$Type (c_ptr) Input
On entry: the handle to the problem. It needs to be initialized (e.g., by e04raf) and must not be changed between calls to the NAG optimization modelling suite.
2: $\mathbf{optstr}$Character(*) Input
On entry: a string identifying the optional parameter whose current value is required. See the documentation of the particular solver for information on valid optional parameters.
3: $\mathbf{ivalue}$Integer Output
On exit: if the optional parameter supplied in optstr is an integer-valued parameter, ivalue will hold its current value.
4: $\mathbf{rvalue}$Real (Kind=nag_wp) Output
On exit: if the optional parameter supplied in optstr is a real-valued parameter, rvalue will hold its current value.
5: $\mathbf{cvalue}$Character(*) Output
Note: the string returned in cvalue will never exceed $40$ characters in length.
On exit: if the optional parameter supplied in optstr is a character-valued parameter, cvalue will hold its current value.
6: $\mathbf{optype}$Integer Output
On exit: indicates whether the optional parameter supplied in optstr is an integer-, real- or character-valued parameter and hence which of ivalue, rvalue or cvalue holds the current value.
${\mathbf{optype}}=1$
optstr is an integer-valued optional parameter; its current value has been returned in ivalue.
${\mathbf{optype}}=2$
optstr is a real-valued optional parameter; its current value has been returned in rvalue.
${\mathbf{optype}}=3$
optstr is a character-valued optional parameter; its current value has been returned in cvalue.
7: $\mathbf{ifail}$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 $-\mathbf{1}$ or $\mathbf{1}$ is used it is essential to test the value of ifail on exit.
On exit: ${\mathbf{ifail}}={\mathbf{0}}$ unless the routine detects an error or a warning has been flagged (see Section 6).

## 6Error Indicators and Warnings

If on entry ${\mathbf{ifail}}=0$ or $-1$, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
${\mathbf{ifail}}=1$
The supplied handle does not define a valid handle to the data structure for the NAG optimization modelling suite. It has not been properly initialized or it has been corrupted.
${\mathbf{ifail}}=11$
On entry, the $\mathit{option}$ supplied in optstr was not recognized: ${\mathbf{optstr}}=⟨\mathit{\text{value}}⟩$.
${\mathbf{ifail}}=41$
On entry, optstr indicates a character optional parameter, but cvalue is too short to hold the stored value. The returned value will be truncated.
${\mathbf{ifail}}=-99$
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.
${\mathbf{ifail}}=-399$
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.
${\mathbf{ifail}}=-999$
Dynamic memory allocation failed.
See Section 9 in the Introduction to the NAG Library FL Interface for further information.

Not applicable.

## 8Parallelism and Performance

e04znf is not threaded in any implementation.