F06FEF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06FEF

Note:  before using this routine, please read the Users' Note for your implementation to check the interpretation of bold italicised terms and other implementation-dependent details.

 Contents

    1  Purpose
    7  Accuracy
    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
x1 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: ALPHA0.0.
3:     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 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.

9  Further Comments

None.

10  Example

None.

F06FEF (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2015