NAG Library Routine Document

f06unf (zlangt)

1
Purpose

f06unf returns, via the function name, the value of the 1-norm, the -norm, the Frobenius norm, or the maximum absolute value of the elements of a complex n by n tridiagonal matrix A.

2
Specification

Fortran Interface
Function f06unf ( norm, n, dl, d, du)
Real (Kind=nag_wp):: f06unf
Integer, Intent (In):: n
Complex (Kind=nag_wp), Intent (In):: dl(*), d(*), du(*)
Character (1), Intent (In):: norm
C Header Interface
#include <nagmk26.h>
double  f06unf_ (const char *norm, const Integer *n, const Complex dl[], const Complex d[], const Complex du[], const Charlen length_norm)

3
Description

None.

4
References

None.

5
Arguments

1:     norm – Character(1)Input
On entry: specifies the value to be returned.
norm='1' or 'O'
The 1-norm.
norm='I'
The -norm.
norm='F' or 'E'
The Frobenius (or Euclidean) norm.
norm='M'
The value maxi,jaij (not a norm).
Constraint: norm='1', 'O', 'I', 'F', 'E' or 'M'.
2:     n – IntegerInput
On entry: n, the order of the matrix A.
When n=0, f06unf returns zero.
Constraint: n0.
3:     dl* – Complex (Kind=nag_wp) arrayInput
Note: the dimension of the array dl must be at least max1,n-1 .
On entry: the (n-1) subdiagonal elements of A.
4:     d* – Complex (Kind=nag_wp) arrayInput
Note: the dimension of the array d must be at least max1,n.
On entry: the n diagonal elements of A.
5:     du* – Complex (Kind=nag_wp) arrayInput
Note: the dimension of the array du must be at least max1,n-1 .
On entry: the (n-1) superdiagonal elements of A.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06unf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.