NAG FL Interface
f06rnf (dlangt)

1 Purpose

f06rnf 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 real n by n tridiagonal matrix A.

2 Specification

Fortran Interface
Function f06rnf ( norm, n, dl, d, du)
Real (Kind=nag_wp) :: f06rnf
Integer, Intent (In) :: n
Real (Kind=nag_wp), Intent (In) :: dl(*), d(*), du(*)
Character (1), Intent (In) :: norm
C Header Interface
#include <nag.h>
double  f06rnf_ (const char *norm, const Integer *n, const double dl[], const double d[], const double du[], const Charlen length_norm)
The routine may be called by the names f06rnf or nagf_blas_dlangt.

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 Integer Input
On entry: n, the order of the matrix A.
When n=0, f06rnf returns zero.
Constraint: n0.
3: dl* Real (Kind=nag_wp) array Input
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* Real (Kind=nag_wp) array Input
Note: the dimension of the array d must be at least max1,n.
On entry: the n diagonal elements of A.
5: du* Real (Kind=nag_wp) array Input
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

f06rnf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.