NAG Library Routine Document

f16ecf (blas_daxpby) (daxpby)

1

Purpose

2

Specification

3

Description

4

References

5

Arguments

1:     $\mathbf{n}$ – IntegerInput

On entry: $n$, the number of elements in $x$ and $y$.

2:     $\mathbf{alpha}$ – Real (Kind=nag_wp)Input

On entry: the scalar $\alpha$.

3:     $\mathbf{x}\left(1+\left(\mathbf{n}-1\right)\times \left|\mathbf{incx}\right|\right)$ – Real (Kind=nag_wp) arrayInput

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

If $\mathbf{incx}>0$, $x_{\mathit{i}}$ must be stored in $\mathbf{x}\left(\left(\mathit{i}-1\right)\times \mathbf{incx}+1\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

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

Intermediate elements of x are not referenced. If $\mathbf{n}=0$, x is not referenced.

4:     $\mathbf{incx}$ – IntegerInput

On entry: the increment in the subscripts of x between successive elements of $x$.

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

5:     $\mathbf{beta}$ – Real (Kind=nag_wp)Input

On entry: the scalar $\beta$.

6:     $\mathbf{y}\left(1+\left(\mathbf{n}-1\right)\times \left|\mathbf{incy}\right|\right)$ – Real (Kind=nag_wp) arrayInput/Output

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

If $\mathbf{incy}>0$, $y_{\mathit{i}}$ must be stored in $\mathbf{y}\left(\left(\mathit{i}-1\right)\times \mathbf{incy}+1\right)$, for $\mathit{i}=1,2,\dots ,\mathbf{n}$.

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

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.

7:     $\mathbf{incy}$ – IntegerInput

On entry: the increment in the subscripts of y between successive elements of $y$.

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

6

Error Indicators and Warnings

7

Accuracy

8

Parallelism and Performance

9

Further Comments

10

Example

10.1

Program Text

Program Text (f16ecfe.f90)

10.2

Program Data

Program Data (f16ecfe.d)

10.3

Program Results

Program Results (f16ecfe.r)