nag_dwaxpby (f16ehc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

NAG Library Function Document

nag_dwaxpby (f16ehc)

+ Contents

    1  Purpose
    7  Accuracy

1  Purpose

nag_dwaxpby (f16ehc) performs scaled vector accumulation, for real vectors and scalars.

2  Specification

#include <nag.h>
#include <nagf16.h>
void  nag_dwaxpby (Integer n, double alpha, const double x[], Integer incx, double beta, const double y[], Integer incy, double w[], Integer incw, NagError *fail)

3  Description

nag_dwaxpby (f16ehc) performs the operation
w αx+βy,
where x and y are n-element real vectors, and α and β are real scalars.

4  References

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

5  Arguments

1:     nIntegerInput
On entry: n, the number of elements in x, y and w.
Constraint: n0.
2:     alphadoubleInput
On entry: the scalar α.
3:     x[dim]const doubleInput
Note: the dimension, dim, of the array x must be at least max1,1+n-1×incx.
On entry: the vector x. Element xi is stored in x[i-1×incx], for i=1,2,,n.
4:     incxIntegerInput
On entry: the increment in the subscripts of x between successive elements of x.
Constraint: incx0.
5:     betadoubleInput
On entry: the scalar β.
6:     y[dim]const doubleInput
Note: the dimension, dim, of the array y must be at least max1,1+n-1×incy.
On entry: the vector y. Element yi is stored in y[i-1×incy], for i=1,2,,n.
7:     incyIntegerInput
On entry: the increment in the subscripts of y between successive elements of y.
Constraint: incy0.
8:     w[dim]doubleOutput
Note: the dimension, dim, of the array w must be at least max1,1+n-1×incw.
On exit: w, the result of the scaled-vector addition. Element wi is stored in w[i-1×incw], for i=1,2,,n.
9:     incwIntegerInput
On entry: the increment in the subscripts of w between successive elements of w.
Constraint: incw0.
10:   failNagError *Input/Output
The NAG error argument (see Section 3.6 in the Essential Introduction).

6  Error Indicators and Warnings

NE_BAD_PARAM
On entry, argument value had an illegal value.
NE_INT
On entry, incw=value.
Constraint: incw0.
On entry, incx=value.
Constraint: incx0.
On entry, incy=value.
Constraint: incy0.
On entry, n=value.
Constraint: n0.

7  Accuracy

Not applicable.

8  Further Comments

None.

9  Example

This example computes the result of a scaled vector accumulation for
α=3,   x = -4,2.1,3.7,4.5,-6T , β=-1,   y = -3,-2.4,6.4,-5,-5.1T .

9.1  Program Text

Program Text (f16ehce.c)

9.2  Program Data

Program Data (f16ehce.d)

9.3  Program Results

Program Results (f16ehce.r)


nag_dwaxpby (f16ehc) (PDF version)
f16 Chapter Contents
f16 Chapter Introduction
NAG C Library Manual

© The Numerical Algorithms Group Ltd, Oxford, UK. 2012