Integer, Intent (In)	::	n
Integer, Intent (Inout)	::	ifail
Real (Kind=nag_wp), Intent (In)	::	a(*)
Character (*), Intent (In)	::	title
Character (1), Intent (In)	::	uplo, diag

C Header Interface

#include <nag.h>

void	x04ccf_ (const char uplo, const char diag, const Integer n, const double a[], const char title, Integer *ifail, const Charlen length_uplo, const Charlen length_diag, const Charlen length_title)

The routine may be called by the names x04ccf or nagf_file_print_matrix_real_packed.

3 Description

x04ccf prints a real triangular matrix stored in packed form. It is an easy-to-use driver for x04cdf. The routine uses default values for the format in which numbers are printed, for labelling the rows and columns, and for output record length. The matrix must be packed by column.

x04ccf will choose a format code such that numbers will be printed with an

F 8.4

, an

F 11.4

or a

1 PE 13.4

format . The

F 8.4

code is chosen if the sizes of all the matrix elements to be printed lie between

0.001

and

1.0

. The

F 11.4

code is chosen if the sizes of all the matrix elements to be printed lie between

0.001

and

9999.9999

. Otherwise the

1 PE 13.4

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: $uplo$ – Character(1) Input

On entry: indicates the type of the matrix to be printed

$uplo ='L'$: The matrix is lower triangular. In this case, the packed array a holds the matrix elements in the following order: $(1, 1), (2, 1), \dots, (n, 1), (2, 2), (3, 2), \dots, (n, 2)$ , etc.
$uplo ='U'$: The matrix is upper triangular. In this case, the packed array a holds the matrix elements in the following order: $(1, 1), (1, 2), (2, 2), (1, 3), (2, 3), (3, 3), (1, 4)$ , etc.

Constraint:

uplo ='L'

'U'

2: $diag$ – Character(1) Input

On entry: indicates 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.

Constraint:

diag ='B'

'U'

'N'

3: $n$ – Integer Input

On entry: the order of the matrix to be printed.

If n is less than

1

, x04ccf will exit immediately after printing title; no row or column labels are printed.

4: $a (*)$ – Real (Kind=nag_wp) array Input

Note: the dimension of the array a must be at least

\max (1, n \times (n + 1) / 2)

On entry: the matrix to be printed. Note that a must have space for the diagonal elements of the matrix, even if these are not stored.

More precisely,

if $uplo ='U'$ , the upper triangle of $A$ must be stored with element $A_{i j}$ in $a (i + j (j - 1) / 2)$ for $i \leq j$ ;
if $uplo ='L'$ , the lower triangle of $A$ must be stored with element $A_{i j}$ in $a (i + (2 n - j) (j - 1) / 2)$ for $i \geq j$ .

diag ='U'

, the diagonal elements of

A

are assumed to be

1

, and are not referenced; the same storage scheme is used whether

diag ='N'

or ‘U’.

5: $title$ – Character(*) Input

On entry: a title to be printed above the matrix.

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.

6: $ifail$ – Integer Input/Output

On entry: ifail must be set to

0

−1

1

to set behaviour on detection of an error; these values have no effect when no error is detected.

A value of

0

causes the printing of an error message and program execution will be halted; otherwise program execution continues. A value of

−1

means that an error message is printed while a value of

1

means that it is not.

If halting is not appropriate, the value

−1

1

is recommended. If message printing is undesirable, then the value

1

is recommended. Otherwise, the value

0

is recommended. 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

−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, uplo is not valid: $uplo = ⟨ value ⟩$ .

$ifail = 2$: On entry, diag is not valid: $diag = ⟨ value ⟩$ .

$ifail = - 99$: An unexpected error has been triggered by this routine. Please contact NAG.
See Section 7 in the Introduction to the NAG Library FL Interface for further information.

$ifail = - 399$: Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library FL Interface for further information.