NAG FL Interface
f06fqf (dsrotg)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{pivot}$ – Character(1) Input

On entry: specifies the plane rotated by $P_k$.

$\mathbf{pivot}=\text{'V'}$ (variable pivot)

$P_k$ rotates the $(k,k+1)$ plane.

$\mathbf{pivot}=\text{'F'}$ (fixed pivot)

$P_k$ rotates the $(1,k+1)$ plane if $\mathbf{direct}=\text{'F'}$, or the $(k,n+1)$ plane if $\mathbf{direct}=\text{'B'}$.

Constraint: $\mathbf{pivot}=\text{'V'}$ or $\text{'F'}$.

2: $\mathbf{direct}$ – Character(1) Input

On entry: specifies the sequence direction.

$\mathbf{direct}=\text{'F'}$ (forward sequence)

$P=P_n\cdots P_2{P}_1$.

$\mathbf{direct}=\text{'B'}$ (backward sequence)

$P=P_1{P}_2\cdots P_n$.

Constraint: $\mathbf{direct}=\text{'F'}$ or $\text{'B'}$.

3: $\mathbf{n}$ – Integer Input

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

4: $\mathbf{alpha}$ – Real (Kind=nag_wp) Input/Output

On entry: the scalar $\alpha$.

On exit: the scalar $\beta$.

5: $\mathbf{x}\left(*\right)$ – Real (Kind=nag_wp) array Input/Output

Note: the dimension of the array x must be at least $\max (1,1+(\mathbf{n}-1)\times \mathbf{incx})$.

On entry: the $n$-element vector $x$. $x_{\mathit{i}}$ must be stored in $\mathbf{x}\left(1+(\mathit{i}-1)\times \mathbf{incx}\right)$, 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 sequence of plane rotations.

6: $\mathbf{incx}$ – Integer Input

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

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

7: $\mathbf{c}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Output

On exit: the values $c_k$, the cosines of the rotations.

8: $\mathbf{s}\left(\mathbf{n}\right)$ – Real (Kind=nag_wp) array Output

On exit: the values $s_k$, the sines of the rotations.

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example