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

5 Arguments

1: $n$ – Integer Input: On entry: $n$ , the number of elements in $x$ and $y$ .

Constraint: $n \geq 0$ .
2: $alpha$ – double Input: On entry: the scalar $α$ .
3: $x [\dim]$ – const double Input: Note: the dimension, dim, of the array x must be at least $\max (1, 1 + (n - 1) \times | incx |)$ .

On entry: the $n$ -element vector $x$ .
If $incx > 0$ , $x_{i}$ must be stored in $x [(i - 1) \times incx]$ , for $i = 1, 2, \dots, n$ .

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

Intermediate elements of x are not referenced. If $n = 0$ , x is not referenced and may be NULL.
4: $incx$ – Integer Input: On entry: the increment in the subscripts of x between successive elements of $x$ .

Constraint: $incx \neq 0$ .
5: $beta$ – double Input: On entry: the scalar $β$ .
6: $y [\dim]$ – double Input/Output: Note: the dimension, dim, of the array y must be at least $\max (1, 1 + (n - 1) \times | incy |)$ .

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

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

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.
7: $incy$ – Integer Input: On entry: the increment in the subscripts of y between successive elements of $y$ .

Constraint: $incy \neq 0$ .
8: $fail$ – 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 $⟨ value ⟩$ had an illegal value.
NE_INT: On entry, $incx = ⟨ value ⟩$ .
Constraint: $incx \neq 0$ .

On entry, $incy = ⟨ value ⟩$ .
Constraint: $incy \neq 0$ .

On entry, $n = ⟨ value ⟩$ .
Constraint: $n \geq 0$ .
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

The BLAS standard requires accurate implementations which avoid unnecessary over/underflow (see Section 2.7 of Basic Linear Algebra Subprograms Technical (BLAST) Forum (2001)).

8 Parallelism and Performance

Background information to multithreading can be found in the Multithreading documentation.

f16ecc makes calls to BLAS and/or LAPACK routines, which may be threaded within the vendor library used by this implementation. Consult the documentation for the vendor library for further information.

Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this function. Please also consult the Users' Note for your implementation for any additional implementation-specific information.

9 Further Comments

None.

10 Example

This example computes the result of a scaled vector accumulation for

\begin{matrix} α = 3, & x = {(−6, 4.5, 3.7, 2.1, −4)}^{T}, \\ β = −1, & y = {(- 5.1, −5, 6.4, - 2.4, −3)}^{T} . \end{matrix}

x

and

y

are stored in reverse order.

f16ec: FL CL CPP AD PY MB

NAG CL Interfacef16ecc (daxpby)

▸▿ Contents

1 Purpose

2 Specification

3 Description

4 References

5 Arguments

6 Error Indicators and Warnings

7 Accuracy

8 Parallelism and Performance

9 Further Comments

10 Example

10.1 Program Text

10.2 Program Data

10.3 Program Results

NAG CL Interface
f16ecc (daxpby)