NAG Library Chapter Introduction
X04 – Input/Output Utilities
1 Scope of the Chapter
This chapter contains utility routines concerned with input and output to or from an external file.
2 Background to the Problems
2.1 Output from NAG Library Routines
Output from NAG Library routines to an external file falls into two categories.
which are always associated with an error exit from a routine, that is, with a nonzero value of IFAIL as specified in Section 6 of the routine document.
which include output of final results, output of intermediate results to monitor the course of a computation, and various warning or informative messages.
Each category of output is written to its own Fortran output unit – the error message unit
or the advisory message unit
. In practice these may be the same unit number. Default unit numbers are provided for each implementation of the Library (see the Users' Note
for your implementation); they may be changed by users. Output of error messages may be controlled by the setting of IFAIL (see Section 3.4.2
in How to Use the NAG Library and its Documentation). Output of advisory messages may usually be controlled by the setting of some other argument (e.g., MSGLVL) (or in some routines also by IFAIL). An alternative mechanism for completely suppressing output is to set the relevant unit number
At present only formatted records are output from the Library. All formatted output to an external file from within the Library is performed by X04BAF
. Similarly, all formatted input from an external file is performed by X04BBF
When the library is being called from another language, such as C or Visual Basic, the routines X04ACF
may be especially useful: X04ACF
connects a file to a FORTRAN unit; X04ADF
disconnects a file from a FORTRAN unit.
2.2 Matrix Printing Routines
Routines are provided to allow formatted output of
||general matrices stored in a two-dimensional array (real, complex and integer data types);
||triangular matrices stored in a packed one-dimensional array (real and complex data types);
||band matrices stored in a packed two-dimensional array (real and complex data types).
Routines in (b)
allow printing of matrices stored in formats used in particular by Chapters F06
of the Library.
By appropriate choice of arguments you can specify titles, labels, maximum output record length, and the format of individual matrix elements. All output is directed to
the advisory messages unit, which may be altered by a call to X04ABF
3 Recommendations on Choice and Use of Available Routines
Apart from the obvious utility of the matrix printing routines, users of the Library may need to call routines in Chapter X04
for the following purposes.
If the default error message unit (given in the Users' Note
for your implementation) is not satisfactory, it may be changed to a new value NERR by the statement
Similarly the advisory message unit may be changed to a new value NADV by the statement
Note that both X04AAF
use a Fortran SAVE statement to retain the value of the unit number and so neither routine is safe to use in a multithreaded environment.
4 Functionality Index
|Accessing external formatted file,|| |
| of advisory message unit|| ||X04ABF|
|Connecting an external file|| ||X04ACF|
|Disconnecting an external file|| ||X04ADF|
| packed complex band matrix|| ||X04DFF|
| packed complex triangular matrix|| ||X04DDF|
| packed real band matrix|| ||X04CFF|
| packed real triangular matrix|| ||X04CDF|
| packed complex band matrix|| ||X04DEF|
| packed complex triangular matrix|| ||X04DCF|
| packed real band matrix|| ||X04CEF|
| packed real triangular matrix|| ||X04CCF|
5 Auxiliary Routines Associated with Library Routine Arguments
6 Routines Withdrawn or Scheduled for Withdrawal