NAG Library Routine Document

f06rpf (dlanst)

1
Purpose

f06rpf 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 symmetric tridiagonal matrix A.

2
Specification

Fortran Interface
Function f06rpf ( norm, n, d, e)
Real (Kind=nag_wp):: f06rpf
Integer, Intent (In):: n
Real (Kind=nag_wp), Intent (In):: d(*), e(*)
Character (1), Intent (In):: norm
C Header Interface
#include <nagmk26.h>
double  f06rpf_ (const char *norm, const Integer *n, const double d[], const double e[], 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, f06rpf returns zero.
Constraint: n0.
3:     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 the tridiagonal matrix A.
4:     e* – Real (Kind=nag_wp) arrayInput
Note: the dimension of the array e must be at least max1,n-1 .
On entry: the (n-1) subdiagonal or superdiagonal elements of the tridiagonal matrix A.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06rpf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.