NAG Library Routine Document

f06fgf  (dnegv)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{n}$ – IntegerInput

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

2:     $\mathbf{x}\left(*\right)$ – 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 vector $-x$ stored in the array elements used to supply the original vector $x$.

Intermediate elements of x are unchanged.

3:     $\mathbf{incx}$ – IntegerInput

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

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

6

Error Indicators and Warnings

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example