NAG Library Routine Document

F06FSF

1  Purpose

2  Specification

3  Description

4  References

5  Parameters

1:     N – INTEGERInput

On entry: $n$, the number of elements in $x$ and $z$.

2:     ALPHA – REAL (KIND=nag_wp)Input/Output

On entry: the scalar $\alpha$.

On exit: the scalar $\beta$.

3:     X($*$) – REAL (KIND=nag_wp) arrayInput/Output

Note: the dimension of the array X must be at least $\max \left(1,1+\left(\mathbf{N}-1\right)\times \mathbf{INCX}\right)$.

On entry: the $n$-element vector $x$. $x_{\mathit{i}}$ must be stored in $\mathbf{X}\left(1+\left(\mathit{i}-1\right)\times \mathbf{INCX}\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{N}$.

Intermediate elements of X are not referenced.

On exit: the referenced elements are overwritten by details of the real elementary reflection.

4:     INCX – INTEGERInput

On entry: the increment in the subscripts of X between successive elements of $x$.

Constraint: $\mathbf{INCX}>0$.

5:     TOL – REAL (KIND=nag_wp)Input

On entry: the value $\mathit{tol}$.

If TOL is not in the range $\left(0,1\right)$, then the value $0$ is used for $\mathit{tol}$.

6:     Z1 – REAL (KIND=nag_wp)Output

On exit: the scalar $\zeta$.

6  Error Indicators and Warnings

7  Accuracy

8  Further Comments

9  Example