F06RNF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06RNF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

+ Contents

    1  Purpose
    7  Accuracy
    9  Example

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

FUNCTION F06RNF ( NORM, N, DL, D, DU)
REAL (KIND=nag_wp) F06RNF
INTEGER  N
REAL (KIND=nag_wp)  DL(*), D(*), DU(*)
CHARACTER(1)  NORM

3  Description

None.

4  References

None.

5  Parameters

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, F06RNF returns zero.
Constraint: N0.
3:     DL(*) – REAL (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(*) – REAL (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(*) – REAL (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  Further Comments

None.

9  Example

None.

F06RNF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012