NAG Library Routine Document

f06fgf  (dnegv)

 Contents

    1  Purpose
    7  Accuracy
    10  Example

1
Purpose

f06fgf negates a real vector.

2
Specification

Fortran Interface
Subroutine f06fgf ( n, x, incx)
Integer, Intent (In):: n, incx
Real (Kind=nag_wp), Intent (Inout):: x(*)
C Header Interface
#include nagmk26.h
void  f06fgf_ ( const Integer *n, double x[], const Integer *incx)

3
Description

f06fgf performs the operation
x-x  
where x is an n-element real vector scattered with stride incx.

4
References

None.

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x.
2:     x* – Real (Kind=nag_wp) arrayInput/Output
Note: the dimension of the array x must be at least max1, 1+n-1 ×incx .
On entry: the n-element vector x. xi must be stored in x1+i-1×incx, for i=1,2,,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:     incx – IntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx>0.

6
Error Indicators and Warnings

None.

7
Accuracy

Not applicable.

8
Parallelism and Performance

f06fgf is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.
© The Numerical Algorithms Group Ltd, Oxford, UK. 2017