NAG Library Routine Document

F06FEF

▸▿ Contents

1 Purpose

2 Specification

3 Description

4 References

5 Parameters

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

1 Purpose

F06FEF multiplies a real vector by the reciprocal of a scalar.

2 Specification

SUBROUTINE F06FEF (

N, ALPHA, X, INCX)

INTEGER	N, INCX
REAL (KIND=nag_wp)	ALPHA, X(*)

3 Description

F06FEF performs the operation

x \leftarrow \frac{1}{α} x

where

x

is an

n

-element real vector scattered with stride INCX and

α

is a real nonzero scalar.

4 References

None.

5 Parameters

1: $N$ – INTEGERInput: On entry: $n$ , the number of elements in $x$ .
2: $ALPHA$ – REAL (KIND=nag_wp)Input: On entry: the scalar $α$ .

Constraint: $ALPHA \neq 0.0$ .
3: $X (*)$ – REAL (KIND=nag_wp) arrayInput/Output: Note: the dimension of the array X must be at least $\max (1, 1 + (N - 1) \times INCX)$ .

On entry: the $n$ -element vector $x$ . $x_{i}$ must be stored in $X (1 + (i - 1) \times INCX)$ , for $i = 1, 2, \dots, N$ .
Intermediate elements of X are not referenced.

On exit: the updated vector $x$ , stored in the same array elements used to supply the original vector.
4: $INCX$ – 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

F06FEF is not threaded by NAG in any implementation.

F06FEF makes calls to BLAS and/or LAPACK routines, which may be threaded within the vendor library used by this implementation. Consult the documentation for the vendor library for further information.

Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this routine. Please also consult the Users' Note for your implementation for any additional implementation-specific information.