E05 Chapter Contents
E05 Chapter Introduction
NAG Library Manual

# NAG Library Routine DocumentE05ZLF

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.

## 1  Purpose

E05ZLF is used to query the value of optional parameters available to supported problem solving routines in Chapter E05. Currently the following routines are supported:

## 2  Specification

 SUBROUTINE E05ZLF ( OPTSTR, IVALUE, RVALUE, CVALUE, OPTYPE, IOPTS, OPTS, IFAIL)
 INTEGER IVALUE, OPTYPE, IOPTS(*), IFAIL REAL (KIND=nag_wp) RVALUE, OPTS(*) CHARACTER(*) OPTSTR, CVALUE

## 3  Description

E05ZLF is used to query the current values of options. It is necessary to initialize optional parameter arrays using E05ZKF before any options are queried.
E05ZLF will normally return either an integer, real or character value dependent upon the type associated with the optional parameter being queried. Some real and integer options also return additional information in CVALUE. Whether the option queried is of integer, real or character type, and whether additional information is returned in CVALUE, is indicated by the returned value of OPTYPE.
Information on optional parameter names and whether these options are real, integer or character can be found in Section 11 in E05SAF, E05SBF, E05UCF and E05USF.

None.

## 5  Parameters

1:     OPTSTR – CHARACTER(*)Input
On entry: a string identifying the option whose current value is required. See Section 11 in E05SAF and E05SBF for information on valid options. In addition, the following is a valid option:
$\mathbf{Identify}$
E05ZLF returns in CVALUE the routine name supplied to E05ZKF when the optional parameter arrays IOPTS and OPTS were initialized.
2:     IVALUE – INTEGEROutput
On exit: if the optional parameter supplied in OPTSTR is an integer valued parameter, IVALUE will hold its current value.
3:     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.
4:     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. CVALUE will also contain additional information for some integer and real valued parameters, as indicated by OPTYPE.
5:     OPTYPE – INTEGEROutput
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.
${\mathbf{OPTYPE}}=4$
OPTSTR is an integer valued optional parameter, its current value has been returned in IVALUE. Additional information has been returned in CVALUE.
${\mathbf{OPTYPE}}=5$
OPTSTR is a real valued optional parameter, its current value has been returned in RVALUE. Additional information has been returned in CVALUE.
6:     IOPTS($*$) – INTEGER arrayCommunication Array
Note: the contents of IOPTS must not have been altered between calls to E05ZKF, E05ZLF and the selected problem solving routine.
7:     OPTS($*$) – REAL (KIND=nag_wp) arrayCommunication Array
Note: the contents of IOPTS must not have been altered between calls to E05ZKF, E05ZLF and the selected problem solving routine.
8:     IFAIL – INTEGERInput/Output
On entry: IFAIL must be set to $0$, $-1\text{​ or ​}1$. 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 $-1\text{​ or ​}1$ 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 $-\mathbf{1}\text{​ or ​}\mathbf{1}$ 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).

## 6  Error Indicators and Warnings

If on entry ${\mathbf{IFAIL}}={\mathbf{0}}$ or $-{\mathbf{1}}$, explanatory error messages are output on the current error message unit (as defined by X04AAF).
Errors or warnings detected by the routine:
${\mathbf{IFAIL}}=11$
On entry, the option in OPTSTR was not recognized.
${\mathbf{IFAIL}}=41$
On entry, OPTSTR identifies a character valued optional parameter. However, CVALUE is too short to contain the entire character string. The value returned in CVALUE will be therefore be truncated.
${\mathbf{IFAIL}}=61$
On entry, either the optional parameter arrays have not been initialized or they have been corrupted.

## 7  Accuracy

Not applicable.

Some options have default values which are problem dependent. For example the option Maximum Iterations Completed for E05SAF has the default value $1000×{\mathbf{NDIM}}$. If options such as this are queried before being set, or before the problem solving routine has been called, they will return misleading information in IVALUE or RVALUE. In some cases, the value of CVALUE will be set to DEFAULT to indicate that the real or integer valued optional parameter supplied in OPTSTR is at its default value.