# NAG C Library Function Document

## 1Purpose

nag_drscl (f06fec) multiplies a real vector by the reciprocal of a scalar.

## 2Specification

 #include #include
 void nag_drscl (Integer n, double alpha, double x[], Integer incx)

## 3Description

nag_drscl (f06fec) performs the operation
 $x←1 α x$
where $x$ is an $n$-element real vector scattered with stride incx and $\alpha$ is a real nonzero scalar.

None.

## 5Arguments

1:    $\mathbf{n}$IntegerInput
On entry: $n$, the number of elements in $x$.
2:    $\mathbf{alpha}$doubleInput
On entry: the scalar $\alpha$.
Constraint: ${\mathbf{alpha}}\ne 0.0$.
3:    $\mathbf{x}\left[\mathit{dim}\right]$doubleInput/Output
Note: the dimension, dim, of the array x must be at least $\mathrm{max}\phantom{\rule{0.125em}{0ex}}\left(1,1+\left({\mathbf{n}}-1\right)×{\mathbf{incx}}\right)$.
On entry: the $n$-element vector $x$. ${x}_{\mathit{i}}$ must be stored in ${\mathbf{x}}\left[1+\left(\mathit{i}-1\right)×{\mathbf{incx}}\right]$, for $\mathit{i}=1,2,\dots ,{\mathbf{n}}$.
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:    $\mathbf{incx}$IntegerInput
On entry: the increment in the subscripts of x between successive elements of $x$.
Constraint: ${\mathbf{incx}}>0$.

None.

Not applicable.

## 8Parallelism and Performance

nag_drscl (f06fec) 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 function. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

None.

None.