NAG Library Routine Document

x04caf  (print_matrix_real_gen)

 Contents

    1  Purpose
    7  Accuracy

1
Purpose

x04caf is an easy-to-use routine to print a real matrix stored in a two-dimensional array.

2
Specification

Fortran Interface
Subroutine x04caf ( matrix, diag, m, n, a, lda, title, ifail)
Integer, Intent (In):: m, n, lda
Integer, Intent (Inout):: ifail
Real (Kind=nag_wp), Intent (In):: a(lda,*)
Character (*), Intent (In):: title
Character (1), Intent (In):: matrix, diag
C Header Interface
#include nagmk26.h
void  x04caf_ ( const char *matrix, const char *diag, const Integer *m, const Integer *n, const double a[], const Integer *lda, const char *title, Integer *ifail, const Charlen length_matrix, const Charlen length_diag, const Charlen length_title)

3
Description

x04caf prints a real matrix. It is an easy-to-use driver for x04cbf. The routine uses default values for the format in which numbers are printed, for labelling the rows and columns, and for output record length.
x04caf will choose a format code such that numbers will be printed with an F8.4, an F11.4 or a 1PE13.4 format. The F8.4 code is chosen if the sizes of all the matrix elements to be printed lie between 0.001 and 1.0. The F11.4 code is chosen if the sizes of all the matrix elements to be printed lie between 0.001 and 9999.9999. Otherwise the 1PE13.4 code is chosen.
The matrix is printed with integer row and column labels, and with a maximum record length of 80.
The matrix is output to the unit defined by x04abf.

4
References

None.

5
Arguments

1:     matrix – Character(1)Input
On entry: indicates the part of the matrix to be printed.
matrix='G'
The whole of the rectangular matrix.
matrix='L'
The lower triangle of the matrix, or the lower trapezium if the matrix has more rows than columns.
matrix='U'
The upper triangle of the matrix, or the upper trapezium if the matrix has more columns than rows.
Constraint: matrix='G', 'L' or 'U'.
2:     diag – Character(1)Input
On entry: unless matrix='G', diag must specify whether the diagonal elements of the matrix are to be printed.
diag='B'
The diagonal elements of the matrix are not referenced and not printed.
diag='U'
The diagonal elements of the matrix are not referenced, but are assumed all to be unity, and are printed as such.
diag='N'
The diagonal elements of the matrix are referenced and printed.
If matrix='G', then diag need not be set.
Constraint: if matrix'G', diag='B', 'U' or 'N'.
3:     m – IntegerInput
4:     n – IntegerInput
On entry: the number of rows and columns of the matrix, respectively, to be printed.
If either m or n is less than 1, x04caf will exit immediately after printing title; no row or column labels are printed.
5:     alda* – Real (Kind=nag_wp) arrayInput
Note: the second dimension of the array a must be at least max1,n.
On entry: the matrix to be printed. Only the elements that will be referred to, as specified by arguments matrix and diag, need be set.
6:     lda – IntegerInput
On entry: the first dimension of the array a as declared in the (sub)program from which x04caf is called.
Constraint: ldamax1,m.
7:     title – Character(*)Input
On entry: a title to be printed above the matrix.
If title=' ', no title (and no blank line) will be printed.
If title contains more than 80 characters, the contents of title will be wrapped onto more than one line, with the break after 80 characters.
Any trailing blank characters in title are ignored.
8:     ifail – IntegerInput/Output
On entry: ifail must be set to 0, -1​ or ​1. If you are unfamiliar with this argument you should refer to Section 3.4 in How to Use the NAG Library and its Documentation for details.
For environments where it might be inappropriate to halt program execution when an error is detected, the value -1​ or ​1 is recommended. If the output of error messages is undesirable, then the value 1 is recommended. Otherwise, if you are not familiar with this argument, the recommended value is 0. When the value -1​ or ​1 is used it is essential to test the value of ifail on exit.
On exit: ifail=0 unless the routine detects an error or a warning has been flagged (see Section 6).

6
Error Indicators and Warnings

If on entry ifail=0 or -1, explanatory error messages are output on the current error message unit (as defined by x04aaf).
Errors or warnings detected by the routine:
ifail=1
On entry,matrix'G', 'L' or 'U'.
ifail=2
On entry,matrix='L' or 'U', but diag'N', 'U' or 'B'.
ifail=3
On entry,lda<m.
ifail=-99
An unexpected error has been triggered by this routine. Please contact NAG.
See Section 3.9 in How to Use the NAG Library and its Documentation for further information.
ifail=-399
Your licence key may have expired or may not have been installed correctly.
See Section 3.8 in How to Use the NAG Library and its Documentation for further information.
ifail=-999
Dynamic memory allocation failed.
See Section 3.7 in How to Use the NAG Library and its Documentation for further information.

7
Accuracy

Not applicable.

8
Parallelism and Performance

x04caf is not threaded in any implementation.

9
Further Comments

A call to x04caf is equivalent to a call to x04cbf with the following argument values:

NCOLS = 80
INDENT = 0
LABROW = 'I'
LABCOL = 'I'
FORM = ' '

10
Example

This example program calls x04caf twice, first to print a 3 by 5 rectangular matrix, and then to print a 5 by 5 lower triangular matrix.

10.1
Program Text

Program Text (x04cafe.f90)

10.2
Program Data

None.

10.3
Program Results

Program Results (x04cafe.r)

© The Numerical Algorithms Group Ltd, Oxford, UK. 2017