NAG FL Interface
f06ecf (daxpy)

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1 Purpose

f06ecf adds a scaled real vector to an unscaled real vector.

2 Specification

Fortran Interface
Subroutine f06ecf ( n, alpha, x, incx, y, incy)
Integer, Intent (In) :: n, incx, incy
Real (Kind=nag_wp), Intent (In) :: alpha, x(*)
Real (Kind=nag_wp), Intent (Inout) :: y(*)
C Header Interface
#include <nag.h>
void  f06ecf_ (const Integer *n, const double *alpha, const double x[], const Integer *incx, double y[], const Integer *incy)
The routine may be called by the names f06ecf, nagf_blas_daxpy or its BLAS name daxpy.

3 Description

f06ecf performs the operation
yαx+y  
where x and y are n-element real vectors scattered with stride incx and incy respectively, 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 Integer Input
On entry: n, the number of elements in x and y.
2: alpha Real (Kind=nag_wp) Input
On entry: the scalar α.
3: x(*) Real (Kind=nag_wp) array Input
Note: the dimension of the array x must be at least max(1, 1+(n-1) ×|incx| ) .
On entry: the n-element vector x.
If incx>0, xi must be stored in x(1+(i-1)×incx), for i=1,2,,n.
If incx<0, xi must be stored in x(1-(n-i)×incx), for i=1,2,,n.
Intermediate elements of x are not referenced.
4: incx Integer Input
On entry: the increment in the subscripts of x between successive elements of x.
5: y(*) Real (Kind=nag_wp) array Input/Output
Note: the dimension of the array y must be at least max(1, 1+(n-1) ×|incy| ) .
On entry: the n-element vector y.
If incy>0, yi must be stored in y(1+(i-1)×incy), for i=1,2,,n.
If incy<0, yi must be stored in y(1-(n-i)×incy), for i=1,2,,n.
Intermediate elements of y are not referenced.
On exit: the updated vector y stored in the array elements used to supply the original vector y.
Intermediate elements of y are unchanged.
6: incy Integer Input
On entry: the increment in the subscripts of y between successive elements of y.

6 Error Indicators and Warnings

None.

7 Accuracy

Not applicable.

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.
f06ecf is not threaded in any implementation.

9 Further Comments

None.

10 Example

None.