# NAG Library Routine Document

## 1Purpose

To supply optional parameters to e04mff/e04mfa from an external file. More precisely, e04mgf must be used to supply optional parameters to e04mff and e04mga must be used to supply optional parameters to e04mfa.
e04mga is a version of e04mgf 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 e04mga.

## 2Specification

### 2.1Specification for e04mgf

Fortran Interface
 Subroutine e04mgf (
 Integer, Intent (In) :: ioptns Integer, Intent (Out) :: inform
#include <nagmk26.h>
 void e04mgf_ (const Integer *ioptns, Integer *inform)

### 2.2Specification for e04mga

Fortran Interface
 Subroutine e04mga (
 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 <nagmk26.h>
 void e04mga_ (const Integer *ioptns, logical lwsav[], Integer iwsav[], double rwsav[], Integer *inform)

## 3Description

e04mgf/e04mga may be used to supply values for optional parameters to e04mff/e04mfa. e04mgf/e04mga 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 e04mgf 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 e04mff or e04mgf and may be turned on again at any time using the keyword List.
For e04mga 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 e04mff/e04mfa 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 e04mff/e04mfa.
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 12 in e04mff/e04mfa.

None.

## 5Arguments

1:     $\mathbf{ioptns}$ – IntegerInput
On entry: the unit number of the options file to be read.
Constraint: $0\le {\mathbf{ioptns}}\le 99$.
2:     $\mathbf{inform}$ – IntegerOutput
Note: for e04mga, 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 e04mga. Users of e04mgf therefore need not read the remainder of this description.
2:     $\mathbf{lwsav}\left(120\right)$ – Logical arrayCommunication Array
3:     $\mathbf{iwsav}\left(610\right)$ – Integer arrayCommunication Array
4:     $\mathbf{rwsav}\left(475\right)$ – Real (Kind=nag_wp) arrayCommunication Array
The arrays lwsav, iwsav and rwsav must not be altered between calls to any of the routines e04mga, e04mfa, e04mha or e04wbf.
5:     $\mathbf{inform}$ – IntegerOutput
Note: see the argument description for inform above.

## 6Error Indicators and Warnings

${\mathbf{inform}}=1$
ioptns is not in the range $\left[0,99\right]$.
${\mathbf{inform}}=2$
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.
${\mathbf{inform}}=4$
Not used.
${\mathbf{inform}}=5$
One or more lines of the options file is invalid. Check that all keywords are neither ambiguous nor misspelt.

Not applicable.

## 8Parallelism and Performance

e04mgf/e04mga is not threaded in any implementation.

e04mhf/e04mha may also be used to supply optional parameters to e04mff/e04mfa.

## 10Example

This example solves the same problem as the example for e04mff/e04mfa, but in addition illustrates the use of e04mgf/e04mga and e04mhf/e04mha to set optional parameters for e04mff/e04mfa.
In this example the options file read by e04mgf/e04mga 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 e04mgf and e04mga.

Program Text (e04mgfe.f90)

Program Text (e04mgae.f90)

### 10.2Program Data

Program Options (e04mgfe.opt)

Program Options (e04mgae.opt)

Program Data (e04mgfe.d)

Program Data (e04mgae.d)

### 10.3Program Results

Program Results (e04mgfe.r)

Program Results (e04mgae.r)