NAG Library Routine Document

f06edf (dscal)

1
Purpose

f06edf (dscal) multiplies a real vector by a real scalar.

2
Specification

Fortran Interface
Subroutine f06edf ( n, alpha, x, incx)
Integer, Intent (In):: n, incx
Real (Kind=nag_wp), Intent (In):: alpha
Real (Kind=nag_wp), Intent (Inout):: x(*)
C Header Interface
#include <nagmk26.h>
void  f06edf_ (const Integer *n, const double *alpha, double x[], const Integer *incx)
The routine may be called by its BLAS name dscal.

3
Description

f06edf (dscal) performs the operation
xαx  
where x is an n-element real vector scattered with stride incx, and α is a real scalar.

4
References

Lawson C L, Hanson R J, Kincaid D R and Krogh F T (1979) Basic linear algebra supbrograms for Fortran usage ACM Trans. Math. Software 5 308–325

5
Arguments

1:     n – IntegerInput
On entry: n, the number of elements in x.
2:     alpha – Real (Kind=nag_wp)Input
On entry: the scalar α.
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 vector αx stored in the array elements used to supply the original vector x.
Intermediate elements of x are unchanged.
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

f06edf (dscal) is not threaded in any implementation.

9
Further Comments

None.

10
Example

None.