NAG Library Manual, Mark 30.1

Interfaces: FL CL CPP AD PY MB

NAG FL Interface Introduction

F06 (Blas) Chapter Contents

F06 (Blas) Chapter Introduction

f06bm: FL CL CPP AD PY MB

NAG FL Interface
f06bmf (dnorm)

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NAG Library Manual, Mark 30.1

Interfaces: FL CL CPP AD PY MB

NAG FL Interface Introduction

F06 (Blas) Chapter Contents

F06 (Blas) Chapter Introduction

f06bm: FL CL CPP AD PY MB

▸▿ Contents

2 Specification

3 Description

4 References

5 Arguments

6 Error Indicators and Warnings

8 Parallelism and Performance

9 Further Comments

© The Numerical Algorithms Group Ltd. 2024

1 Purpose

f06bmf completes the safe computation of the Euclidean length of a vector, following a call to f06fjf or f06kjf.

2 Specification

Fortran Interface

Function f06bmf (

Real (Kind=nag_wp)	::	f06bmf
Real (Kind=nag_wp), Intent (In)	::	scal, ssq

C Header Interface

#include <nag.h>

double

f06bmf_ (const double *scal, const double *ssq)

The routine may be called by the names f06bmf or nagf_blas_dnorm.

3 Description

f06bmf completes the safe computation of the Euclidean length of a vector, following a call to f06fjf or f06kjf which return values

α

and

ξ

such that

{‖ x ‖}_{2}^{2} = α^{2} ξ .

f06bmf returns, via the function name, the value

\min (α \sqrt{ξ}, flmax),

where

flmax

is the value given by

1 / (x02amf)

.

4 References

None.

5 Arguments

1: $scal$ – Real (Kind=nag_wp) Input: On entry: the scaling factor $α$ , returned by f06fjf or f06kjf.

Constraint: $scal \geq 0.0$ .
2: $ssq$ – Real (Kind=nag_wp) Input: On entry: the scaled sum of squares $ξ$ , returned by f06fjf or f06kjf.

Constraint: $ssq \geq 1.0$ .

6 Error Indicators and Warnings

None.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.

f06bmf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.

NAG Library Manual, Mark 30.1

Interfaces: FL CL CPP AD PY MB

NAG FL Interface Introduction

F06 (Blas) Chapter Contents

F06 (Blas) Chapter Introduction

f06bm: FL CL CPP AD PY MB

© The Numerical Algorithms Group Ltd. 2024