F06ECF (DAXPY) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

NAG Library Routine Document

F06ECF (DAXPY)

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
    9  Example

1  Purpose

F06ECF (DAXPY) adds a scaled real vector to an unscaled real vector.

2  Specification

SUBROUTINE F06ECF ( N, ALPHA, X, INCX, Y, INCY)
INTEGER  N, INCX, INCY
REAL (KIND=nag_wp)  ALPHA, X(*), Y(*)
The routine may be called by its BLAS name daxpy.

3  Description

F06ECF (DAXPY) 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  Parameters

1:     N – INTEGERInput
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) arrayInput
Note: the dimension of the array X must be at least max1, 1+N-1 ×INCX .
On entry: the n-element vector x.
If INCX>0, xi must be stored in X1+i-1×INCX, for i=1,2,,N.
If INCX<0, xi must be stored in X1-N-i×INCX, for i=1,2,,N.
Intermediate elements of X are not referenced.
4:     INCX – INTEGERInput
On entry: the increment in the subscripts of X between successive elements of x.
5:     Y(*) – REAL (KIND=nag_wp) arrayInput/Output
Note: the dimension of the array Y must be at least max1, 1+N-1 ×INCY .
On entry: the n-element vector y.
If INCY>0, yi must be stored in Y1+i-1×INCY, for i=1,2,,N.
If INCY<0, yi must be stored in Y1-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 – INTEGERInput
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  Further Comments

None.

9  Example

None.

F06ECF (DAXPY) (PDF version)
F06 Chapter Contents
F06 Chapter Introduction
NAG Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012