NAG CL Interface
f16eac (ddot)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{conj}$ – Nag_ConjType Input

On entry: conj is not used. The presence of this argument in the BLAST standard is for consistency with the interface of the complex variant of this function.

Constraint: $\mathbf{conj}=\mathrm{Nag\_NoConj}$ or $\mathrm{Nag\_Conj}$.

2: $\mathbf{n}$ – Integer Input

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

3: $\mathbf{alpha}$ – double Input

On entry: the scalar $\alpha$.

4: $\mathbf{x}\left[1+(\mathbf{n}-1)\times \left|\mathbf{incx}\right|\right]$ – const double Input

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

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

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

Intermediate elements of x are not referenced. If $\alpha =0.0$ or $\mathbf{n}=0$, x is not referenced and may be NULL.

5: $\mathbf{incx}$ – Integer Input

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

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

6: $\mathbf{beta}$ – double Input

On entry: the scalar $\beta$.

7: $\mathbf{y}\left[1+(\mathbf{n}-1)\times \left|\mathbf{incy}\right|\right]$ – const double Input

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

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

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

Intermediate elements of y are not referenced. If $\alpha =0.0$ or $\mathbf{n}=0$, y is not referenced and may be NULL.

8: $\mathbf{incy}$ – Integer Input

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

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

9: $\mathbf{r}$ – double * Input/Output

On entry: the initial value, $r$, to be updated. If $\beta =0.0$, r need not be set on entry.

On exit: the value $r$, scaled by $\beta$ and updated by the scaled dot product of $x$ and $y$.

10: $\mathbf{fail}$ – NagError * Input/Output

The NAG error argument (see Section 7 in the Introduction to the NAG Library CL Interface).

6 Error Indicators and Warnings

NE_ALLOC_FAIL

Dynamic memory allocation failed.
See Section 3.1.2 in the Introduction to the NAG Library CL Interface for further information.

NE_BAD_PARAM

On entry, argument $⟨\mathit{\text{value}}⟩$ had an illegal value.

NE_INT

On entry, $\mathbf{incx}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{incx}\ne 0$.

On entry, $\mathbf{incy}=⟨\mathit{\text{value}}⟩$.
Constraint: $\mathbf{incy}\ne 0$.

NE_NO_LICENCE

Your licence key may have expired or may not have been installed correctly.
See Section 8 in the Introduction to the NAG Library CL Interface for further information.

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results