# NAG FL Interfacee04udf  (nlp1_option_file_old)e04uda (nlp1_option_file)

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## 1Purpose

To supply optional parameters to e04ucf/​e04uca from an external file. More precisely, e04udf must be used to supply optional parameters to e04ucf and e04uda must be used to supply optional parameters to e04uca.
e04uda is a version of e04udf that has additional arguments in order to make it safe for use in multithreaded applications (see Section 5). The initialization routine e04wbf must have been called before calling e04uda.
e04udf/​e04uda can also be used to supply optional parameters to e04uff/​e04ufa.

## 2Specification

### 2.1Specification for e04udf

Fortran Interface
 Subroutine e04udf (
 Integer, Intent (In) :: ioptns Integer, Intent (Out) :: inform
#include <nag.h>
 void e04udf_ (const Integer *ioptns, Integer *inform)

### 2.2Specification for e04uda

Fortran Interface
 Subroutine e04uda (
 Integer, Intent (In) :: ioptns Integer, Intent (Inout) :: iwsav(610) Integer, Intent (Out) :: inform Real (Kind=nag_wp), Intent (Inout) :: rwsav(475) Logical, Intent (Inout) :: lwsav(120)
#include <nag.h>
 void e04uda_ (const Integer *ioptns, logical lwsav[], Integer iwsav[], double rwsav[], Integer *inform)

## 3Description

e04udf/​e04uda may be used to supply values for optional parameters to e04ucf/​e04uca. e04udf/​e04uda reads an external file and each line of the file defines a single optional parameter. It is only necessary to supply values for those arguments whose values are to be different from their default values.
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.
Blank strings and comments are ignored. A comment begins with an asterisk (*) and all subsequent characters in the string are regarded as part of the comment.
The file containing the options must start with Begin and must finish with End. An example of a valid options file is:
```Begin * Example options file
Print level = 5
End```
For e04udf each line of the file is normally printed as it is read, on the current advisory message unit (see x04abf), but printing may be suppressed using the keyword Nolist. To suppress printing of Begin, Nolist must be the first option supplied as in the file:
```Begin
Nolist
Print level = 5
End```
Printing will automatically be turned on again after a call to e04ucf or e04udf and may be turned on again at any time using the keyword List.
For e04uda printing is turned off by default, but may be turned on at any time using the keyword List.
Optional parameter settings are preserved following a call to e04ucf/​e04uca 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 e04ucf/​e04uca.
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in e04ucf/​e04uca.

None.

## 5Arguments

1: $\mathbf{ioptns}$Integer Input
On entry: the unit number of the options file to be read.
Constraint: $0\le {\mathbf{ioptns}}\le 2147483647$.
2: $\mathbf{inform}$Integer Output
Note: for e04uda, inform does not occur in this position in the argument list. See the additional arguments described below.
On exit: contains zero if the options file has been successfully read and a $\text{value}>0$; otherwise, (see Section 6).
Note: the following are additional arguments for specific use with e04uda. Users of e04udf therefore need not read the remainder of this description.
2: $\mathbf{lwsav}\left(120\right)$Logical array Communication Array
3: $\mathbf{iwsav}\left(610\right)$Integer array Communication Array
4: $\mathbf{rwsav}\left(475\right)$Real (Kind=nag_wp) array Communication Array
The arrays lwsav, iwsav and rwsav must not be altered between calls to any of the routines e04uda, e04uca, e04uea and e04wbf.
5: $\mathbf{inform}$Integer Output
Note: see the argument description for inform above.

## 6Error Indicators and Warnings

${\mathbf{inform}}=1$
On entry, ${\mathbf{ioptns}}=⟨\mathit{\text{value}}⟩$.
Constraint: $0\le {\mathbf{ioptns}}\le 2147483647$.
${\mathbf{inform}}=2$
Begin was found, but end-of-file was found before End was found.
${\mathbf{inform}}=3$
End-of-file was found before Begin was found.
${\mathbf{inform}}=5$
One or more lines of the options file is invalid. Check that the keywords are neither ambiguous nor misspelt.

Not applicable.

## 8Parallelism and Performance

e04udf/​e04uda is not threaded in any implementation.

e04uef/​e04uea may also be used to supply optional parameters to e04ucf/​e04uca.

## 10Example

This example solves the same problem as the example for e04ucf/​e04uca, but in addition illustrates the use of e04udf/​e04uda and e04uef/​e04uea to set optional parameters for e04ucf/​e04uca.
In this example the options file read by e04udf/​e04uda is appended to the data file for the program (see Section 10.2). It would usually be more convenient in practice to keep the data file and the options file separate.

### 10.1Program Text

Note: the following programs illustrate the use of e04udf and e04uda.
Program Text (e04udfe.f90)
Program Text (e04udae.f90)

### 10.2Program Data

Program Options (e04udfe.opt)
Program Options (e04udae.opt)
Program Data (e04udfe.d)
Program Data (e04udae.d)

### 10.3Program Results

Program Results (e04udfe.r)
Program Results (e04udae.r)