naginterfaces.library.blast.daxpby

naginterfaces.library.blast.daxpby(alpha, x, beta, y)

daxpby computes the sum of two scaled vectors, for real vectors and scalars.

For full information please refer to the NAG Library document for f16ec

https://support.nag.com/numeric/nl/nagdoc_30.3/flhtml/f16/f16ecf.html

Parameters

alphafloat

The scalar $\alpha$.

xfloat, array-like, shape $\left(n\right)$

The $n$-element vector $x$.

If $\text{incx}<0$, $x_{\text{i}}$ must be stored in $x[(n-\text{i})\times \left|\text{incx}\right|]$, for $\text{i}=1,2,\dots ,n$.

If $n=0$, $x$ is not referenced.

betafloat

The scalar $\beta$.

yfloat, ndarray, shape $\left(n\right)$, modified in place

On entry: the $n$-element vector $y$.

If $\text{incy}>0$, $y_{\text{i}}$ must be stored in $y[(\text{i}-1)\times \text{incy}]$, for $\text{i}=1,2,\dots ,n$.

If $\text{incy}<0$, $y_{\text{i}}$ must be stored in $y[(n-\text{i})\times \left|\text{incy}\right|]$, for $\text{i}=1,2,\dots ,n$.

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.

Raises

NagValueError

(errno $-4$)

On entry, error in parameter $\text{incx}$.

Constraint: $\text{incx}\ne 0$.

(errno $-7$)

On entry, error in parameter $\text{incy}$.

Constraint: $\text{incy}\ne 0$.

Notes

daxpby performs the operation

$$y\leftarrow \alpha x+\beta y$$

where $x$ and $y$ are $n$-element real vectors, and $\alpha$ and $\beta$ real scalars. If $n$ is equal to zero, or if $\alpha$ is equal to zero and $\beta$ is equal to $1$, this function returns immediately.

References

Basic Linear Algebra Subprograms Technical (BLAST) Forum, 2001, Basic Linear Algebra Subprograms Technical (BLAST) Forum Standard, University of Tennessee, Knoxville, Tennessee, https://www.netlib.org/blas/blast-forum/blas-report.pdf