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NAG FL Interface
f06unf (zlangt)

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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×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 <nag.h>
double  f06unf_ (const char *norm, const Integer *n, const Complex dl[], const Complex d[], const Complex du[], const Charlen length_norm)
The routine may be called by the names f06unf or nagf_blas_zlangt.

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,j|aij| (not a norm).
Constraint: norm='1', 'O', 'I', 'F', 'E' or 'M'.
2: n Integer Input
On entry: n, the order of the matrix A.
When n=0, f06unf returns zero.
Constraint: n0.
3: dl(*) Complex (Kind=nag_wp) array Input
Note: the dimension of the array dl must be at least max(1,n-1) .
On entry: the (n-1) subdiagonal elements of A.
4: d(*) Complex (Kind=nag_wp) array Input
Note: the dimension of the array d must be at least max(1,n).
On entry: the n diagonal elements of A.
5: du(*) Complex (Kind=nag_wp) array Input
Note: the dimension of the array du must be at least max(1,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.