F06FKF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06FKF

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

F06FKF computes the weighted Euclidean norm of a real vector.

2  Specification

FUNCTION F06FKF ( N, W, INCW, X, INCX)
REAL (KIND=nag_wp) F06FKF
INTEGER  N, INCW, INCX
REAL (KIND=nag_wp)  W(*), X(*)

3  Description

F06FKF returns, via the function name, the weighted Euclidean norm
xTWx
of the n-element real vector x scattered with stride INCW and INCX respectively, where W=diagw and w is a vector of weights scattered with stride INCW.

4  References

None.

5  Parameters

1:     N – INTEGERInput
On entry: n, the number of elements in x.
2:     W(*) – REAL (KIND=nag_wp) arrayInput
Note: the dimension of the array W must be at least max1, 1+N-1 ×INCW .
On entry: w, the vector of weights.
If INCW>0, wi must be stored in W1+i-1×INCX, for i=1,2,,N.
If INCW<0, wi must be stored in W1-N-i×INCW, for i=1,2,,N.
Constraint: All weights must be non-negative.
3:     INCW – INTEGERInput
On entry: the increment in the subscripts of W between successive elements of w.
4:     X(*) – REAL (KIND=nag_wp) arrayInput
Note: the dimension of the array X must be at least max1, 1+N-1 ×INCX .
On entry: the n-element vector x.
If INCX>0, xi must be stored in X1+i-1×INCX, for i=1,2,,N.
If INCX<0, xi must be stored in X1-N-i×INCX, for i=1,2,,N.
Intermediate elements of X are not referenced.
5:     INCX – INTEGERInput
On entry: the increment in the subscripts of X between successive elements of x.

6  Error Indicators and Warnings

None.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

None.

F06FKF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

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