NAG Library Routine Document
E04WEF may be used to supply optional parameters to E04WDF
from an external file. The initialization routine E04WCF must
have been called before calling E04WEF.
||ISPECS, IW(*), IFAIL
E04WEF may be used to supply values for optional parameters to
. E04WEF reads an external file
line of the file defines a single optional parameter. It is only necessary to supply values for those parameters whose values are to be different from their default values.
Each optional parameter is defined by a single character string,
of up to
consisting of one or more items. The items associated with a given option must be separated by spaces, or equals signs
. 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 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
Optional parameter settings are preserved following a call to E04WDF
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 E04WDF
A complete list of optional parameters, their abbreviations, synonyms and default values is given in Section 11
Hock W and Schittkowski K (1981) Test Examples for Nonlinear Programming Codes. Lecture Notes in Economics and Mathematical Systems 187 Springer–Verlag
- 1: ISPECS – INTEGERInput
On entry: the unit number of the option file to be read.
is a valid unit open for reading.
- 2: IW() – INTEGER arrayCommunication Array
the dimension of the array IW
must be at least
- 3: RW() – REAL (KIND=nag_wp) arrayCommunication Array
the dimension of the array RW
must be at least
- 4: IFAIL – INTEGERInput/Output
must be set to
. 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
is recommended. If the output of error messages is undesirable, then the value
is recommended. Otherwise, if you are not familiar with this parameter, the recommended value is
. When the value is used it is essential to test the value of IFAIL on exit.
unless the routine detects an error or a warning has been flagged (see Section 6
6 Error Indicators and Warnings
If on entry
, explanatory error messages are output on the current error message unit (as defined by X04AAF
Errors or warnings detected by the routine:
The initialization routine E04WCF
has not been called.
Could not read options file on unit ISPECS
. This may be due to:
||ISPECS is not a valid unit number;
||a file is not associated with unit ISPECS, or if it is, is unavailable for read access;
||one or more lines of the options file is invalid. Check that all keywords are neither ambiguous nor misspelt;
||Begin was found, but end-of-file was found before End was found;
||end-of-file was found before Begin was found.
may also be used to supply optional parameters to
This example is based on Problem 71 in Hock and Schittkowski (1981)
and involves the minimization of the nonlinear function
subject to the bounds
to the general linear constraint
and to the nonlinear constraints
The initial point, which is infeasible, is
The optimal solution (to five figures) is
. One bound constraint and both nonlinear constraints are active at the solution.
The document for E04WEF includes an example program to solve the same problem using some of the optional parameters described in Section 11
9.1 Program Text
Program Text (e04wefe.f90)
9.2 Program Data
Program Data (e04wefe.d)
Program Options (e04wefe.opt)
9.3 Program Results
Program Results (e04wefe.r)