# NAG FL Interfacee04vlf (nlp2_​sparse_​option_​string)

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## 1Purpose

e04vlf may be used to supply individual optional parameters to e04vhf. The initialization routine e04vgf must have been called before calling e04vlf.

## 2Specification

Fortran Interface
 Subroutine e04vlf ( cw, iw, rw,
 Integer, Intent (Inout) :: iw(*), ifail Real (Kind=nag_wp), Intent (Inout) :: rw(*) Character (*), Intent (In) :: string Character (8), Intent (InOut) :: cw(*)
#include <nag.h>
 void e04vlf_ (const char *st, char cw[], Integer iw[], double rw[], Integer *ifail, const Charlen length_st, const Charlen length_cw)
The routine may be called by the names e04vlf or nagf_opt_nlp2_sparse_option_string.

## 3Description

e04vlf may be used to supply values for optional parameters to e04vhf. It is only necessary to call e04vlf for those arguments whose values are to be different from their default values. One call to e04vlf sets one argument value.
Each optional parameter is defined by a single character string, of up to $72$ characters, consisting of one or more items. The items associated with a given option must be separated by spaces, or equals signs $\left[=\right]$. Alphabetic characters may be upper or lower case. The string
`Print Level = 1`
is an example of a string used to set an optional parameter. For each option the string contains one or more of the following items:
• a mandatory keyword;
• a phrase that qualifies the keyword;
• a number that specifies an integer or real value. Such numbers may be up to $40$ contiguous characters in Fortran's I, F, E or D formats, terminated by a space if this is not the last item on the line.
For e04vlf, each user-specified option is not normally printed as it is defined, but this printing may be turned on using the keyword List. Thus the statement
`Call e04vlf ('List', cw, iw, rw, ifail)`
turns on printing of this and subsequent options. Printing may be turned off again using the keyword Nolist.
Optional parameter settings are preserved following a call to e04vhf and so the keyword Defaults is provided to allow you to reset all the optional parameters to their default values before a subsequent call to e04vhf.
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in e04vhf.

None.

## 5Arguments

1: $\mathbf{string}$Character(*) Input
On entry: a single valid option string (see Section 3 in e04vlf and Section 12 in e04vhf).
2: $\mathbf{cw}\left(*\right)$Character(8) array Communication Array
Note: the actual argument supplied must be the array cw supplied to the initialization routine e04vgf.
3: $\mathbf{iw}\left(*\right)$Integer array Communication Array
Note: the actual argument supplied must be the array iw supplied to the initialization routine e04vgf.
4: $\mathbf{rw}\left(*\right)$Real (Kind=nag_wp) array Communication Array
Note: the actual argument supplied must be the array rw supplied to the initialization routine e04vgf.
5: $\mathbf{ifail}$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 initialization routine e04vgf has not been called.
${\mathbf{ifail}}=2$
The supplied option is invalid. Check that the keywords are neither ambiguous nor misspelt. The option string is ‘$⟨\mathit{\text{value}}⟩$’.
${\mathbf{ifail}}=-99$
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

e04vlf is not threaded in any implementation.