# NAG C Library Function Document

## 1Purpose

nag_opt_nlp_option_set_string (e04wfc) may be used to supply individual optional parameters to nag_opt_nlp_solve (e04wdc). The initialization function nag_opt_nlp_init (e04wcc) must have been called before calling nag_opt_nlp_option_set_string (e04wfc).

## 2Specification

 #include #include
 void nag_opt_nlp_option_set_string (const char *string, Nag_E04State *state, NagError *fail)

## 3Description

nag_opt_nlp_option_set_string (e04wfc) may be used to supply values for optional parameters to nag_opt_nlp_solve (e04wdc). It is only necessary to call nag_opt_nlp_option_set_string (e04wfc) for those arguments whose values are to be different from their default values. One call to nag_opt_nlp_option_set_string (e04wfc) sets one argument value.
Each optional parameter is defined by a single character string, 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 double value. Such numbers may be up to $40$ contiguous characters which can be read using C's d or g formats, terminated by a space if this is not the last item on the line.
For nag_opt_nlp_option_set_string (e04wfc), each user-specified option is not normally printed as it is defined, but this printing may be turned on using the keyword ${\mathbf{List}}$. Thus the statement
```e04wfc ("List", &state, &fail);
```
turns on printing of this and subsequent options. Printing may be turned off again using the keyword ${\mathbf{Nolist}}$.
Optional parameter settings are preserved following a call to nag_opt_nlp_solve (e04wdc) and so the keyword ${\mathbf{Defaults}}$ is provided to allow you to reset all the optional parameters to their default values before a subsequent call to nag_opt_nlp_solve (e04wdc).
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in nag_opt_nlp_solve (e04wdc).

None.

## 5Arguments

1:    $\mathbf{string}$const char *Input
On entry: a single valid option string (see Section 3 in nag_opt_nlp_option_set_string (e04wfc) and Section 12 in nag_opt_nlp_solve (e04wdc)).
2:    $\mathbf{state}$Nag_E04State *Communication Structure
state contains internal information required for functions in this suite. It must not be modified in any way.
3:    $\mathbf{fail}$NagError *Input/Output
The NAG error argument (see Section 3.7 in How to Use the NAG Library and its Documentation).

## 6Error Indicators and Warnings

NE_ALLOC_FAIL
Dynamic memory allocation failed.
See Section 2.3.1.2 in How to Use the NAG Library and its Documentation for further information.
On entry, argument $〈\mathit{\text{value}}〉$ had an illegal value.
NE_E04_OPTION_INVALID
The supplied option is invalid. Check that the keywords are neither ambiguous nor misspelt. The option string is ‘$〈\mathit{\text{value}}〉$’.
NE_E04WCC_NOT_INIT
The initialization function nag_opt_nlp_init (e04wcc) has not been called.
NE_INTERNAL_ERROR
An internal error has occurred in this function. Check the function call and any array sizes. If the call is correct then please contact NAG for assistance.
See Section 2.7.6 in How to Use the NAG Library and its Documentation for further information.
NE_NO_LICENCE
Your licence key may have expired or may not have been installed correctly.
See Section 2.7.5 in How to Use the NAG Library and its Documentation for further information.

Not applicable.

## 8Parallelism and Performance

nag_opt_nlp_option_set_string (e04wfc) is not threaded in any implementation.