NAG CL Interface
f16pec (dspmv)

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

1: $\mathbf{order}$ – Nag_OrderType Input

On entry: the order argument specifies the two-dimensional storage scheme being used, i.e., row-major ordering or column-major ordering. C language defined storage is specified by $\mathbf{order}=\mathrm{Nag\_RowMajor}$. See Section 3.1.3 in the Introduction to the NAG Library CL Interface for a more detailed explanation of the use of this argument.

Constraint: $\mathbf{order}=\mathrm{Nag\_RowMajor}$ or $\mathrm{Nag\_ColMajor}$.

2: $\mathbf{uplo}$ – Nag_UploType Input

On entry: specifies whether the upper or lower triangular part of $A$ is stored.

$\mathbf{uplo}=\mathrm{Nag\_Upper}$

The upper triangular part of $A$ is stored.

$\mathbf{uplo}=\mathrm{Nag\_Lower}$

The lower triangular part of $A$ is stored.

Constraint: $\mathbf{uplo}=\mathrm{Nag\_Upper}$ or $\mathrm{Nag\_Lower}$.

3: $\mathbf{n}$ – Integer Input

On entry: $n$, the order of the matrix $A$.

Constraint: $\mathbf{n}\ge 0$.

4: $\mathbf{alpha}$ – double Input

On entry: the scalar $\alpha$.

5: $\mathbf{ap}\left[\mathit{dim}\right]$ – const double Input

Note: the dimension, dim, of the array ap must be at least $\max (1,\mathbf{n}\times (\mathbf{n}+1)/2)$.

On entry: the $n\times n$ symmetric matrix $A$, packed by rows or columns.

The storage of elements $A_{ij}$ depends on the order and uplo arguments as follows:

if $\mathbf{order}=\mathrm{Nag\_ColMajor}$ and $\mathbf{uplo}=\mathrm{Nag\_Upper}$,

$A_{ij}$ is stored in $\mathbf{ap}\left[(j-1)\times j/2+i-1\right]$, for $i\le j$;

if $\mathbf{order}=\mathrm{Nag\_ColMajor}$ and $\mathbf{uplo}=\mathrm{Nag\_Lower}$,

$A_{ij}$ is stored in $\mathbf{ap}\left[(2n-j)\times (j-1)/2+i-1\right]$, for $i\ge j$;

if $\mathbf{order}=\mathrm{Nag\_RowMajor}$ and $\mathbf{uplo}=\mathrm{Nag\_Upper}$,

$A_{ij}$ is stored in $\mathbf{ap}\left[(2n-i)\times (i-1)/2+j-1\right]$, for $i\le j$;

if $\mathbf{order}=\mathrm{Nag\_RowMajor}$ and $\mathbf{uplo}=\mathrm{Nag\_Lower}$,

$A_{ij}$ is stored in $\mathbf{ap}\left[(i-1)\times i/2+j-1\right]$, for $i\ge j$.

6: $\mathbf{x}\left[\mathit{dim}\right]$ – const double Input

Note: the dimension, dim, of the array x must be at least $\max (1,1+(\mathbf{n}-1)\left|\mathbf{incx}\right|)$.

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 $\mathbf{n}=0$, x is not referenced and may be NULL.

7: $\mathbf{incx}$ – Integer Input

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

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

8: $\mathbf{beta}$ – double Input

On entry: the scalar $\beta$.

9: $\mathbf{y}\left[\mathit{dim}\right]$ – double Input/Output

Note: the dimension, dim, of the array y must be at least $\max (1,1+(\mathbf{n}-1)\left|\mathbf{incy}\right|)$.

On entry: the vector $y$. See x for details of storage.

If $\mathbf{beta}=0$, y need not be set.

On exit: the updated vector $y$.

10: $\mathbf{incy}$ – Integer Input

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

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

11: $\mathbf{fail}$ – 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: $\mathbf{incy}\ne 0$.

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

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